# Ternary Search

• Difficulty Level : Easy
• Last Updated : 20 Jun, 2022

Ternary search is a decrease(by constant) and conquer algorithm that can be used to find an element in an array. It is similar to binary search where we divide the array into two parts but in this algorithm, we divide the given array into three parts and determine which has the key (searched element). We can divide the array into three parts by taking mid1 and mid2 which can be calculated as shown below. Initially, l and r will be equal to 0 and n-1 respectively, where n is the length of the array.

It is same as the binary search. The only difference is that, it reduces the time complexity a bit more. Its time complexity is O(log n base 3) and that of binary search is O(log n base 2).

mid1 = l + (r-l)/3
mid2 = r – (r-l)/3

Note: Array needs to be sorted to perform ternary search on it.

Steps to perform Ternary Search:

1. First, we compare the key with the element at mid1. If found equal, we return mid1.
2. If not, then we compare the key with the element at mid2. If found equal, we return mid2.
3. If not, then we check whether the key is less than the element at mid1. If yes, then recur to the first part.
4. If not, then we check whether the key is greater than the element at mid2. If yes, then recur to the third part.
5. If not, then we recur to the second (middle) part. Example: Recursive Implementation of Ternary Search

## C++

 `// C++ program to illustrate ` `// recursive approach to ternary search ` `#include ` `using` `namespace` `std; ` ` `  `// Function to perform Ternary Search ` `int` `ternarySearch(``int` `l, ``int` `r, ``int` `key, ``int` `ar[]) ` `{ ` `    ``if` `(r >= l) { ` ` `  `        ``// Find the mid1 and mid2 ` `        ``int` `mid1 = l + (r - l) / 3; ` `        ``int` `mid2 = r - (r - l) / 3; ` ` `  `        ``// Check if key is present at any mid ` `        ``if` `(ar[mid1] == key) { ` `            ``return` `mid1; ` `        ``} ` `        ``if` `(ar[mid2] == key) { ` `            ``return` `mid2; ` `        ``} ` ` `  `        ``// Since key is not present at mid, ` `        ``// check in which region it is present ` `        ``// then repeat the Search operation ` `        ``// in that region ` `        ``if` `(key < ar[mid1]) { ` ` `  `            ``// The key lies in between l and mid1 ` `            ``return` `ternarySearch(l, mid1 - 1, key, ar); ` `        ``} ` `        ``else` `if` `(key > ar[mid2]) { ` ` `  `            ``// The key lies in between mid2 and r ` `            ``return` `ternarySearch(mid2 + 1, r, key, ar); ` `        ``} ` `        ``else` `{ ` ` `  `            ``// The key lies in between mid1 and mid2 ` `            ``return` `ternarySearch(mid1 + 1, mid2 - 1, key, ar); ` `        ``} ` `    ``} ` ` `  `    ``// Key not found ` `    ``return` `-1; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `l, r, p, key; ` ` `  `    ``// Get the array ` `    ``// Sort the array if not sorted ` `    ``int` `ar[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; ` ` `  `    ``// Starting index ` `    ``l = 0; ` ` `  `    ``// length of array ` `    ``r = 9; ` ` `  `    ``// Checking for 5 ` ` `  `    ``// Key to be searched in the array ` `    ``key = 5; ` ` `  `    ``// Search the key using ternarySearch ` `    ``p = ternarySearch(l, r, key, ar); ` ` `  `    ``// Print the result ` `    ``cout << ``"Index of "` `<< key ` `         ``<< ``" is "` `<< p << endl; ` ` `  `    ``// Checking for 50 ` ` `  `    ``// Key to be searched in the array ` `    ``key = 50; ` ` `  `    ``// Search the key using ternarySearch ` `    ``p = ternarySearch(l, r, key, ar); ` ` `  `    ``// Print the result ` `    ``cout << ``"Index of "` `<< key ` `         ``<< ``" is "` `<< p << endl; ` `} ` ` `  `// This code is contributed ` `// by Akanksha_Rai `

## C

 `// C program to illustrate ` `// recursive approach to ternary search ` ` `  `#include ` ` `  `// Function to perform Ternary Search ` `int` `ternarySearch(``int` `l, ``int` `r, ``int` `key, ``int` `ar[]) ` `{ ` `    ``if` `(r >= l) { ` ` `  `        ``// Find the mid1 and mid2 ` `        ``int` `mid1 = l + (r - l) / 3; ` `        ``int` `mid2 = r - (r - l) / 3; ` ` `  `        ``// Check if key is present at any mid ` `        ``if` `(ar[mid1] == key) { ` `            ``return` `mid1; ` `        ``} ` `        ``if` `(ar[mid2] == key) { ` `            ``return` `mid2; ` `        ``} ` ` `  `        ``// Since key is not present at mid, ` `        ``// check in which region it is present ` `        ``// then repeat the Search operation ` `        ``// in that region ` ` `  `        ``if` `(key < ar[mid1]) { ` ` `  `            ``// The key lies in between l and mid1 ` `            ``return` `ternarySearch(l, mid1 - 1, key, ar); ` `        ``} ` `        ``else` `if` `(key > ar[mid2]) { ` ` `  `            ``// The key lies in between mid2 and r ` `            ``return` `ternarySearch(mid2 + 1, r, key, ar); ` `        ``} ` `        ``else` `{ ` ` `  `            ``// The key lies in between mid1 and mid2 ` `            ``return` `ternarySearch(mid1 + 1, mid2 - 1, key, ar); ` `        ``} ` `    ``} ` ` `  `    ``// Key not found ` `    ``return` `-1; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `l, r, p, key; ` ` `  `    ``// Get the array ` `    ``// Sort the array if not sorted ` `    ``int` `ar[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; ` ` `  `    ``// Starting index ` `    ``l = 0; ` ` `  `    ``// length of array ` `    ``r = 9; ` ` `  `    ``// Checking for 5 ` ` `  `    ``// Key to be searched in the array ` `    ``key = 5; ` ` `  `    ``// Search the key using ternarySearch ` `    ``p = ternarySearch(l, r, key, ar); ` ` `  `    ``// Print the result ` `    ``printf``(``"Index of %d is %d\n"``, key, p); ` ` `  `    ``// Checking for 50 ` ` `  `    ``// Key to be searched in the array ` `    ``key = 50; ` ` `  `    ``// Search the key using ternarySearch ` `    ``p = ternarySearch(l, r, key, ar); ` ` `  `    ``// Print the result ` `    ``printf``(``"Index of %d is %d"``, key, p); ` `} `

## Java

 `// Java program to illustrate ` `// recursive approach to ternary search ` ` `  `class` `GFG { ` ` `  `    ``// Function to perform Ternary Search ` `    ``static` `int` `ternarySearch(``int` `l, ``int` `r, ``int` `key, ``int` `ar[]) ` `    ``{ ` `        ``if` `(r >= l) { ` ` `  `            ``// Find the mid1 and mid2 ` `            ``int` `mid1 = l + (r - l) / ``3``; ` `            ``int` `mid2 = r - (r - l) / ``3``; ` ` `  `            ``// Check if key is present at any mid ` `            ``if` `(ar[mid1] == key) { ` `                ``return` `mid1; ` `            ``} ` `            ``if` `(ar[mid2] == key) { ` `                ``return` `mid2; ` `            ``} ` ` `  `            ``// Since key is not present at mid, ` `            ``// check in which region it is present ` `            ``// then repeat the Search operation ` `            ``// in that region ` ` `  `            ``if` `(key < ar[mid1]) { ` ` `  `                ``// The key lies in between l and mid1 ` `                ``return` `ternarySearch(l, mid1 - ``1``, key, ar); ` `            ``} ` `            ``else` `if` `(key > ar[mid2]) { ` ` `  `                ``// The key lies in between mid2 and r ` `                ``return` `ternarySearch(mid2 + ``1``, r, key, ar); ` `            ``} ` `            ``else` `{ ` ` `  `                ``// The key lies in between mid1 and mid2 ` `                ``return` `ternarySearch(mid1 + ``1``, mid2 - ``1``, key, ar); ` `            ``} ` `        ``} ` ` `  `        ``// Key not found ` `        ``return` `-``1``; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``int` `l, r, p, key; ` ` `  `        ``// Get the array ` `        ``// Sort the array if not sorted ` `        ``int` `ar[] = { ``1``, ``2``, ``3``, ``4``, ``5``, ``6``, ``7``, ``8``, ``9``, ``10` `}; ` ` `  `        ``// Starting index ` `        ``l = ``0``; ` ` `  `        ``// length of array ` `        ``r = ``9``; ` ` `  `        ``// Checking for 5 ` ` `  `        ``// Key to be searched in the array ` `        ``key = ``5``; ` ` `  `        ``// Search the key using ternarySearch ` `        ``p = ternarySearch(l, r, key, ar); ` ` `  `        ``// Print the result ` `        ``System.out.println(``"Index of "` `+ key + ``" is "` `+ p); ` ` `  `        ``// Checking for 50 ` ` `  `        ``// Key to be searched in the array ` `        ``key = ``50``; ` ` `  `        ``// Search the key using ternarySearch ` `        ``p = ternarySearch(l, r, key, ar); ` ` `  `        ``// Print the result ` `        ``System.out.println(``"Index of "` `+ key + ``" is "` `+ p); ` `    ``} ` `} `

## Python3

 `# Python3 program to illustrate ` `# recursive approach to ternary search ` `import` `math as mt ` ` `  `# Function to perform Ternary Search ` `def` `ternarySearch(l, r, key, ar): ` ` `  `    ``if` `(r >``=` `l): ` ` `  `        ``# Find the mid1 and mid2 ` `        ``mid1 ``=` `l ``+` `(r ``-` `l) ``/``/``3` `        ``mid2 ``=` `r ``-` `(r ``-` `l) ``/``/``3` ` `  `        ``# Check if key is present at any mid ` `        ``if` `(ar[mid1] ``=``=` `key):  ` `            ``return` `mid1 ` `         `  `        ``if` `(ar[mid2] ``=``=` `key):  ` `            ``return` `mid2 ` `         `  `        ``# Since key is not present at mid, ` `        ``# check in which region it is present ` `        ``# then repeat the Search operation ` `        ``# in that region ` `        ``if` `(key < ar[mid1]):  ` ` `  `            ``# The key lies in between l and mid1 ` `            ``return` `ternarySearch(l, mid1 ``-` `1``, key, ar) ` `         `  `        ``elif` `(key > ar[mid2]):  ` ` `  `            ``# The key lies in between mid2 and r ` `            ``return` `ternarySearch(mid2 ``+` `1``, r, key, ar) ` `         `  `        ``else``:  ` ` `  `            ``# The key lies in between mid1 and mid2 ` `            ``return` `ternarySearch(mid1 ``+` `1``,  ` `                                 ``mid2 ``-` `1``, key, ar) ` `         `  `    ``# Key not found ` `    ``return` `-``1` ` `  `# Driver code ` `l, r, p ``=` `0``, ``9``, ``5` ` `  `# Get the array ` `# Sort the array if not sorted ` `ar ``=` `[ ``1``, ``2``, ``3``, ``4``, ``5``, ``6``, ``7``, ``8``, ``9``, ``10` `] ` ` `  `# Starting index ` `l ``=` `0` ` `  `# length of array ` `r ``=` `9` ` `  `# Checking for 5 ` ` `  `# Key to be searched in the array ` `key ``=` `5` ` `  `# Search the key using ternarySearch ` `p ``=` `ternarySearch(l, r, key, ar) ` ` `  `# Print the result ` `print``(``"Index of"``, key, ``"is"``, p) ` ` `  `# Checking for 50 ` ` `  `# Key to be searched in the array ` `key ``=` `50` ` `  `# Search the key using ternarySearch ` `p ``=` `ternarySearch(l, r, key, ar) ` ` `  `# Print the result ` `print``(``"Index of"``, key, ``"is"``, p) ` ` `  `# This code is contributed by  ` `# Mohit kumar 29 `

## C#

 `// CSharp program to illustrate ` `// recursive approach to ternary search ` `using` `System; ` ` `  `class` `GFG { ` ` `  `    ``// Function to perform Ternary Search ` `    ``static` `int` `ternarySearch(``int` `l, ``int` `r, ``int` `key, ``int``[] ar) ` `    ``{ ` `        ``if` `(r >= l) { ` ` `  `            ``// Find the mid1 and mid2 ` `            ``int` `mid1 = l + (r - l) / 3; ` `            ``int` `mid2 = r - (r - l) / 3; ` ` `  `            ``// Check if key is present at any mid ` `            ``if` `(ar[mid1] == key) { ` `                ``return` `mid1; ` `            ``} ` `            ``if` `(ar[mid2] == key) { ` `                ``return` `mid2; ` `            ``} ` ` `  `            ``// Since key is not present at mid, ` `            ``// check in which region it is present ` `            ``// then repeat the Search operation ` `            ``// in that region ` ` `  `            ``if` `(key < ar[mid1]) { ` ` `  `                ``// The key lies in between l and mid1 ` `                ``return` `ternarySearch(l, mid1 - 1, key, ar); ` `            ``} ` `            ``else` `if` `(key > ar[mid2]) { ` ` `  `                ``// The key lies in between mid2 and r ` `                ``return` `ternarySearch(mid2 + 1, r, key, ar); ` `            ``} ` `            ``else` `{ ` ` `  `                ``// The key lies in between mid1 and mid2 ` `                ``return` `ternarySearch(mid1 + 1, mid2 - 1, key, ar); ` `            ``} ` `        ``} ` ` `  `        ``// Key not found ` `        ``return` `-1; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``int` `l, r, p, key; ` ` `  `        ``// Get the array ` `        ``// Sort the array if not sorted ` `        ``int``[] ar = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; ` ` `  `        ``// Starting index ` `        ``l = 0; ` ` `  `        ``// length of array ` `        ``r = 9; ` ` `  `        ``// Checking for 5 ` ` `  `        ``// Key to be searched in the array ` `        ``key = 5; ` ` `  `        ``// Search the key using ternarySearch ` `        ``p = ternarySearch(l, r, key, ar); ` ` `  `        ``// Print the result ` `        ``Console.WriteLine(``"Index of "` `+ key + ``" is "` `+ p); ` ` `  `        ``// Checking for 50 ` ` `  `        ``// Key to be searched in the array ` `        ``key = 50; ` ` `  `        ``// Search the key using ternarySearch ` `        ``p = ternarySearch(l, r, key, ar); ` ` `  `        ``// Print the result ` `        ``Console.WriteLine(``"Index of "` `+ key + ``" is "` `+ p); ` `    ``} ` `} ` ` `  `// This code is contributed by Ryuga `

## PHP

 `= ``\$l``) ` `    ``{ ` ` `  `        ``// Find the mid1 and mid2 ` `        ``\$mid1` `= (int)(``\$l` `+ (``\$r` `- ``\$l``) / 3); ` `        ``\$mid2` `= (int)(``\$r` `- (``\$r` `- ``\$l``) / 3); ` ` `  `        ``// Check if key is present at any mid ` `        ``if` `(``\$ar``[``\$mid1``] == ``\$key``)  ` `        ``{ ` `            ``return` `\$mid1``; ` `        ``} ` `        ``if` `(``\$ar``[``\$mid2``] == ``\$key``) ` `        ``{ ` `            ``return` `\$mid2``; ` `        ``} ` ` `  `        ``// Since key is not present at mid, ` `        ``// check in which region it is present ` `        ``// then repeat the Search operation ` `        ``// in that region ` `        ``if` `(``\$key` `< ``\$ar``[``\$mid1``])  ` `        ``{ ` ` `  `            ``// The key lies in between l and mid1 ` `            ``return` `ternarySearch(``\$l``, ``\$mid1` `- 1,  ` `                                     ``\$key``, ``\$ar``); ` `        ``} ` `        ``else` `if` `(``\$key` `> ``\$ar``[``\$mid2``])  ` `        ``{ ` ` `  `            ``// The key lies in between mid2 and r ` `            ``return` `ternarySearch(``\$mid2` `+ 1, ``\$r``,      ` `                                 ``\$key``, ``\$ar``); ` `        ``} ` `        ``else` `        ``{ ` ` `  `            ``// The key lies in between mid1 and mid2 ` `            ``return` `ternarySearch(``\$mid1` `+ 1, ``\$mid2` `- 1, ` `                                            ``\$key``, ``\$ar``); ` `        ``} ` `    ``} ` ` `  `    ``// Key not found ` `    ``return` `-1; ` `} ` ` `  `// Driver code ` ` `  `// Get the array ` `// Sort the array if not sorted ` `\$ar` `= ``array``( 1, 2, 3, 4, 5,  ` `             ``6, 7, 8, 9, 10 ); ` ` `  `// Starting index ` `\$l` `= 0; ` ` `  `// length of array ` `\$r` `= 9; ` ` `  `// Checking for 5 ` ` `  `// Key to be searched in the array ` `\$key` `= 5; ` ` `  `// Search the key using ternarySearch ` `\$p` `= ternarySearch(``\$l``, ``\$r``, ``\$key``, ``\$ar``); ` ` `  `// Print the result ` `echo` `"Index of "``, ``\$key``, ` `     ``" is "``, (int)``\$p``, ``"\n"``; ` ` `  `// Checking for 50 ` ` `  `// Key to be searched in the array ` `\$key` `= 50; ` ` `  `// Search the key using ternarySearch ` `\$p` `= ternarySearch(``\$l``, ``\$r``, ``\$key``, ``\$ar``); ` ` `  `// Print the result ` `echo` `"Index of "``, ``\$key``,  ` `     ``" is "``, (int)``\$p``, ``"\n"``; ` ` `  `// This code is contributed by Arnab Kundu ` `?> `

## Javascript

 ``

Output:

```Index of 5 is 4
Index of 50 is -1```

Time Complexity: O(log3n)

Auxiliary Space: O(log3n)

Iterative Approach of Ternary Search

## C++

 `// C++ program to illustrate ` `// iterative approach to ternary search ` ` `  `#include ` `using` `namespace` `std; ` ` `  `// Function to perform Ternary Search ` `int` `ternarySearch(``int` `l, ``int` `r, ``int` `key, ``int` `ar[]) ` ` `  `{ ` `    ``while` `(r >= l) { ` ` `  `        ``// Find the mid1 and mid2 ` `        ``int` `mid1 = l + (r - l) / 3; ` `        ``int` `mid2 = r - (r - l) / 3; ` ` `  `        ``// Check if key is present at any mid ` `        ``if` `(ar[mid1] == key) { ` `            ``return` `mid1; ` `        ``} ` `        ``if` `(ar[mid2] == key) { ` `            ``return` `mid2; ` `        ``} ` ` `  `        ``// Since key is not present at mid, ` `        ``// check in which region it is present ` `        ``// then repeat the Search operation ` `        ``// in that region ` ` `  `        ``if` `(key < ar[mid1]) { ` ` `  `            ``// The key lies in between l and mid1 ` `            ``r = mid1 - 1; ` `        ``} ` `        ``else` `if` `(key > ar[mid2]) { ` ` `  `            ``// The key lies in between mid2 and r ` `            ``l = mid2 + 1; ` `        ``} ` `        ``else` `{ ` ` `  `            ``// The key lies in between mid1 and mid2 ` `            ``l = mid1 + 1; ` `            ``r = mid2 - 1; ` `        ``} ` `    ``} ` ` `  `    ``// Key not found ` `    ``return` `-1; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `l, r, p, key; ` ` `  `    ``// Get the array ` `    ``// Sort the array if not sorted ` `    ``int` `ar[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; ` ` `  `    ``// Starting index ` `    ``l = 0; ` ` `  `    ``// length of array ` `    ``r = 9; ` ` `  `    ``// Checking for 5 ` ` `  `    ``// Key to be searched in the array ` `    ``key = 5; ` ` `  `    ``// Search the key using ternarySearch ` `    ``p = ternarySearch(l, r, key, ar); ` ` `  `    ``// Print the result ` `    ``cout << ``"Index of "``<

## C

 `// C program to illustrate ` `// iterative approach to ternary search ` ` `  `#include ` ` `  `// Function to perform Ternary Search ` `int` `ternarySearch(``int` `l, ``int` `r, ``int` `key, ``int` `ar[]) ` ` `  `{ ` `    ``while` `(r >= l) { ` ` `  `        ``// Find the mid1 and mid2 ` `        ``int` `mid1 = l + (r - l) / 3; ` `        ``int` `mid2 = r - (r - l) / 3; ` ` `  `        ``// Check if key is present at any mid ` `        ``if` `(ar[mid1] == key) { ` `            ``return` `mid1; ` `        ``} ` `        ``if` `(ar[mid2] == key) { ` `            ``return` `mid2; ` `        ``} ` ` `  `        ``// Since key is not present at mid, ` `        ``// check in which region it is present ` `        ``// then repeat the Search operation ` `        ``// in that region ` ` `  `        ``if` `(key < ar[mid1]) { ` ` `  `            ``// The key lies in between l and mid1 ` `            ``r = mid1 - 1; ` `        ``} ` `        ``else` `if` `(key > ar[mid2]) { ` ` `  `            ``// The key lies in between mid2 and r ` `            ``l = mid2 + 1; ` `        ``} ` `        ``else` `{ ` ` `  `            ``// The key lies in between mid1 and mid2 ` `            ``l = mid1 + 1; ` `            ``r = mid2 - 1; ` `        ``} ` `    ``} ` ` `  `    ``// Key not found ` `    ``return` `-1; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `l, r, p, key; ` ` `  `    ``// Get the array ` `    ``// Sort the array if not sorted ` `    ``int` `ar[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; ` ` `  `    ``// Starting index ` `    ``l = 0; ` ` `  `    ``// length of array ` `    ``r = 9; ` ` `  `    ``// Checking for 5 ` ` `  `    ``// Key to be searched in the array ` `    ``key = 5; ` ` `  `    ``// Search the key using ternarySearch ` `    ``p = ternarySearch(l, r, key, ar); ` ` `  `    ``// Print the result ` `    ``printf``(``"Index of %d is %d\n"``, key, p); ` ` `  `    ``// Checking for 50 ` ` `  `    ``// Key to be searched in the array ` `    ``key = 50; ` ` `  `    ``// Search the key using ternarySearch ` `    ``p = ternarySearch(l, r, key, ar); ` ` `  `    ``// Print the result ` `    ``printf``(``"Index of %d is %d"``, key, p); ` `} `

## Java

 `// Java program to illustrate ` `// the iterative approach to ternary search ` ` `  `class` `GFG { ` ` `  `    ``// Function to perform Ternary Search ` `    ``static` `int` `ternarySearch(``int` `l, ``int` `r, ``int` `key, ``int` `ar[]) ` ` `  `    ``{ ` `        ``while` `(r >= l) { ` ` `  `            ``// Find the mid1  mid2 ` `            ``int` `mid1 = l + (r - l) / ``3``; ` `            ``int` `mid2 = r - (r - l) / ``3``; ` ` `  `            ``// Check if key is present at any mid ` `            ``if` `(ar[mid1] == key) { ` `                ``return` `mid1; ` `            ``} ` `            ``if` `(ar[mid2] == key) { ` `                ``return` `mid2; ` `            ``} ` ` `  `            ``// Since key is not present at mid, ` `            ``// check in which region it is present ` `            ``// then repeat the Search operation ` `            ``// in that region ` ` `  `            ``if` `(key < ar[mid1]) { ` ` `  `                ``// The key lies in between l and mid1 ` `                ``r = mid1 - ``1``; ` `            ``} ` `            ``else` `if` `(key > ar[mid2]) { ` ` `  `                ``// The key lies in between mid2 and r ` `                ``l = mid2 + ``1``; ` `            ``} ` `            ``else` `{ ` ` `  `                ``// The key lies in between mid1 and mid2 ` `                ``l = mid1 + ``1``; ` `                ``r = mid2 - ``1``; ` `            ``} ` `        ``} ` ` `  `        ``// Key not found ` `        ``return` `-``1``; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``int` `l, r, p, key; ` ` `  `        ``// Get the array ` `        ``// Sort the array if not sorted ` `        ``int` `ar[] = { ``1``, ``2``, ``3``, ``4``, ``5``, ``6``, ``7``, ``8``, ``9``, ``10` `}; ` ` `  `        ``// Starting index ` `        ``l = ``0``; ` ` `  `        ``// length of array ` `        ``r = ``9``; ` ` `  `        ``// Checking for 5 ` ` `  `        ``// Key to be searched in the array ` `        ``key = ``5``; ` ` `  `        ``// Search the key using ternarySearch ` `        ``p = ternarySearch(l, r, key, ar); ` ` `  `        ``// Print the result ` `        ``System.out.println(``"Index of "` `+ key + ``" is "` `+ p); ` ` `  `        ``// Checking for 50 ` ` `  `        ``// Key to be searched in the array ` `        ``key = ``50``; ` ` `  `        ``// Search the key using ternarySearch ` `        ``p = ternarySearch(l, r, key, ar); ` ` `  `        ``// Print the result ` `        ``System.out.println(``"Index of "` `+ key + ``" is "` `+ p); ` `    ``} ` `} `

## Python3

 `# Python 3 program to illustrate iterative ` `# approach to ternary search ` ` `  `# Function to perform Ternary Search ` `def` `ternarySearch(l, r, key, ar): ` `    ``while` `r >``=` `l: ` `         `  `        ``# Find mid1 and mid2 ` `        ``mid1 ``=` `l ``+` `(r``-``l) ``/``/` `3` `        ``mid2 ``=` `r ``-` `(r``-``l) ``/``/` `3` ` `  `        ``# Check if key is at any mid ` `        ``if` `key ``=``=` `ar[mid1]: ` `            ``return` `mid1 ` `        ``if` `key ``=``=` `mid2: ` `            ``return` `mid2 ` ` `  `        ``# Since key is not present at mid,  ` `        ``# Check in which region it is present ` `        ``# Then repeat the search operation in that region ` `        ``if` `key < ar[mid1]: ` `            ``# key lies between l and mid1 ` `            ``r ``=` `mid1 ``-` `1` `        ``elif` `key > ar[mid2]: ` `            ``# key lies between mid2 and r ` `            ``l ``=` `mid2 ``+` `1` `        ``else``: ` `            ``# key lies between mid1 and mid2 ` `            ``l ``=` `mid1 ``+` `1` `            ``r ``=` `mid2 ``-` `1` ` `  `    ``# key not found ` `    ``return` `-``1` ` `  `# Driver code ` ` `  `# Get the list ` `# Sort the list if not sorted ` `ar ``=` `[``1``, ``2``, ``3``, ``4``, ``5``, ``6``, ``7``, ``8``, ``9``, ``10``] ` ` `  `# Starting index ` `l ``=` `0` ` `  `# Length of list ` `r ``=` `9` ` `  `# Checking for 5 ` `# Key to be searched in the list ` `key ``=` `5` ` `  `# Search the key using ternary search ` `p ``=` `ternarySearch(l, r, key, ar) ` ` `  `# Print the result ` `print``(``"Index of"``, key, ``"is"``, p) ` ` `  `# Checking for 50 ` `# Key to be searched in the list ` `key ``=` `50` ` `  `# Search the key using ternary search ` `p ``=` `ternarySearch(l, r, key, ar) ` ` `  `# Print the result ` `print``(``"Index of"``, key, ``"is"``, p) ` ` `  `# This code has been contributed by Sujal Motagi `

## C#

 `// C# program to illustrate the iterative ` `// approach to ternary search ` `using` `System; ` ` `  `public` `class` `GFG { ` ` `  `    ``// Function to perform Ternary Search ` `    ``static` `int` `ternarySearch(``int` `l, ``int` `r, ` `                             ``int` `key, ``int``[] ar) ` ` `  `    ``{ ` `        ``while` `(r >= l) { ` ` `  `            ``// Find the mid1 and mid2 ` `            ``int` `mid1 = l + (r - l) / 3; ` `            ``int` `mid2 = r - (r - l) / 3; ` ` `  `            ``// Check if key is present at any mid ` `            ``if` `(ar[mid1] == key) { ` `                ``return` `mid1; ` `            ``} ` `            ``if` `(ar[mid2] == key) { ` `                ``return` `mid2; ` `            ``} ` ` `  `            ``// Since key is not present at mid, ` `            ``// check in which region it is present ` `            ``// then repeat the Search operation ` `            ``// in that region ` ` `  `            ``if` `(key < ar[mid1]) { ` ` `  `                ``// The key lies in between l and mid1 ` `                ``r = mid1 - 1; ` `            ``} ` `            ``else` `if` `(key > ar[mid2]) { ` ` `  `                ``// The key lies in between mid2 and r ` `                ``l = mid2 + 1; ` `            ``} ` `            ``else` `{ ` ` `  `                ``// The key lies in between mid1 and mid2 ` `                ``l = mid1 + 1; ` `                ``r = mid2 - 1; ` `            ``} ` `        ``} ` ` `  `        ``// Key not found ` `        ``return` `-1; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main(String[] args) ` `    ``{ ` `        ``int` `l, r, p, key; ` ` `  `        ``// Get the array ` `        ``// Sort the array if not sorted ` `        ``int``[] ar = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; ` ` `  `        ``// Starting index ` `        ``l = 0; ` ` `  `        ``// length of array ` `        ``r = 9; ` ` `  `        ``// Checking for 5 ` ` `  `        ``// Key to be searched in the array ` `        ``key = 5; ` ` `  `        ``// Search the key using ternarySearch ` `        ``p = ternarySearch(l, r, key, ar); ` ` `  `        ``// Print the result ` `        ``Console.WriteLine(``"Index of "` `+ key + ``" is "` `+ p); ` ` `  `        ``// Checking for 50 ` ` `  `        ``// Key to be searched in the array ` `        ``key = 50; ` ` `  `        ``// Search the key using ternarySearch ` `        ``p = ternarySearch(l, r, key, ar); ` ` `  `        ``// Print the result ` `        ``Console.WriteLine(``"Index of "` `+ key + ``" is "` `+ p); ` `    ``} ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

## Javascript

 ``

Output:

```Index of 5 is 4
Index of 50 is -1```

Time Complexity: O(log3n), where n is the size of the array.

Auxiliary Space: O(1)

## Binary search Vs Ternary Search

The time complexity of the binary search is more than  the ternary search but it does not mean that ternary search is better. In reality, the number of comparisons in ternary search much more which makes it slower than binary search.

Uses: In finding the maximum or minimum of a unimodal function.
Hackerearth Problems on Ternary search

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