# Find duplicates under given constraints

• Difficulty Level : Basic
• Last Updated : 09 Mar, 2022

A sorted array contains 6 different numbers, only 1 number is repeated five times. So there are total 10 numbers in array. Find the duplicate numbers using two comparisons only.
Examples :

```Input: arr[] = {1, 1, 1, 1, 1, 5, 7, 10, 20, 30}
Output: 1

Input: arr[] = {1, 2, 3, 3, 3, 3, 3, 5, 9, 10}
Output: 3```

An important observation is, arr or arr is an occurrence of repeated element for sure. Below is the implementation based on this observation.

## CPP

 `// C++ program to find duplicate element under` `// given constraints.` `#include` `using` `namespace` `std;`   `// This function assumes array is sorted,  has` `// 10 elements,  there are total 6 different` `// elements and one element repeats 5 times.` `int` `findDuplicate(``int` `a[])` `{` `    ``if` `(a == a)` `        ``return` `a;` `    ``else` `if` `(a == a)` `        ``return` `a;` `    ``else` `        ``return` `a;` `}`   `// Driver code` `int` `main()` `{` `    ``int` `a[] = {1, 1, 1, 1, 1, 5, 7, 10, 20, 30};` `    ``cout << findDuplicate(a);` `    ``return` `0;` `}`

## JAVA

 `// Java program to find duplicate element under` `// given constraints.` `class` `Num{`   `// This function assumes array is sorted, has` `// 10 elements, there are total 6 different` `// elements and one element repeats 5 times.` `static` `int` `findDuplicate(``int` `a[])` `{` `    ``if` `(a[``3``] == a[``4``])` `        ``return` `a[``3``];` `    ``else` `if` `(a[``4``] == a[``5``])` `        ``return` `a[``4``];` `    ``else` `        ``return` `a[``5``];` `}`   `// Driver code` `public` `static` `void` `main(String[] args)` `{` `    ``int` `a[] = {``1``, ``1``, ``1``, ``1``, ``1``, ``5``, ``7``, ``10``, ``20``, ``30``};` `    ``System.out.println(findDuplicate(a));` `}` `}` `//This code is contributed by` `//Smitha Dinesh Semwal`

## Python3

 `# Python 3 program to find duplicate` `# element under given constraints.`   `# This function assumes array is ` `# sorted, has 10 elements, there are` `# total 6 different elements and one` `# element repeats 5 times.` `def` `findDuplicate(a):`   `    ``if` `(a[``3``] ``=``=` `a[``4``]):` `        ``return` `a[``3``] ` `    ``else` `if` `(a[``4``] ``=``=` `a[``5``]):` `        ``return` `a[``4``] ` `    ``else``:` `        ``return` `a[``5``] `   `# Driver code` `a ``=` `[``1``, ``1``, ``1``, ``1``, ``1``, ``5``, ``7``,` `              ``10``, ``20``, ``30``] `   `print``(findDuplicate(a)) `   `# This code is contributed by Smitha Dinesh Semwal`

## C#

 `// C# program to find duplicate  ` `// element under given constraints.` `using` `System;`   `class` `GFG {`   `// This function assumes array is ` `// sorted, has 10 elements, there` `// are total 6 different elements` `// and one element repeats 5 times.` `static` `int` `findDuplicate(``int` `[]a)` `{` `    ``if` `(a == a)` `        ``return` `a;` `    ``else` `if` `(a == a)` `        ``return` `a;` `    ``else` `        ``return` `a;` `}`   `// Driver code` `public` `static` `void` `Main()` `{` `    ``int` `[]a = {1, 1, 1, 1, 1, 5,` `               ``7, 10, 20, 30};` `    ``Console.Write(findDuplicate(a));` `}` `}`   `// This code is contributed by nitin mittal`

## PHP

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## Javascript

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Output :

`1`

Exercise: Extend the above problem for an array with n different elements, size of array is 2*(n-1) and one element repeats (n-1) times.
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