# Find the length of Longest increasing Consecutive Subarray

• Last Updated : 01 Feb, 2022

Given an array arr[] of N integers, the task is to find the length of the longest increasing subarray such that elements in the subarray are consecutive integers.

Examples:

Input: arr[] = {1, 9, 3, 4, 20, 2}
Output: 2
Explanation: The subarray {3, 4} is the longest subarray of consecutive elements

Input: arr[] = {36, 41, 56, 32, 33, 34, 35, 43, 32, 42}
Output: 4
Explanation: The subarray {32, 33, 34, 35} is the longest subarray of consecutive elements

Approach: The idea is to run a loop and keep a count and max (both initially zero). Follow the steps mentioned below:

• Run a loop from start to end.
• If the current element is not equal to the (previous element+1) then set the count to 1.
• Else increase the count.
• Update max with a maximum of count and max.

Below is the implementation of the above approach.

## C++

 `// C++ program to find longest` `// increasing consecutive subarray` `#include ` `using` `namespace` `std;`   `// Returns length of the longest` `// consecutive subarray` `int` `findLongestConseqSubarr(vector<``int``>& v)` `{` `    ``int` `ans = 0, count = 0;`   `    ``// find the maximum length` `    ``// by traversing the array` `    ``for` `(``int` `i = 0; i < v.size(); i++) {`   `        ``// Check if the current element ` `        ``// is equal to previous element + 1` `        ``if` `(i > 0 && v[i] == v[i - 1] + 1)` `            ``count++;` `        ``// reset the count` `        ``else` `            ``count = 1;`   `        ``// update the maximum` `        ``ans = max(ans, count);` `    ``}` `    ``return` `ans;` `}`   `// Driver code` `int` `main()` `{` `    ``vector<``int``> arr = { 1, 9, 3, 4, 20, 2 };` `    ``cout << findLongestConseqSubarr(arr);` `    ``return` `0;` `}`

## Java

 `// Java program for the above approach` `import` `java.io.*;` `import` `java.lang.*;` `import` `java.util.*;`   `class` `GFG {`   `  ``// Returns length of the longest` `  ``// consecutive subarray` `  ``static` `int` `findLongestConseqSubarr(``int`  `arr[ ])` `  ``{` `    ``int` `ans = ``0``, count = ``0``;`   `    ``// find the maximum length` `    ``// by traversing the array` `    ``for` `(``int` `i = ``0``; i < arr.length; i++) {`   `      ``// Check if the current element ` `      ``// is equal to previous element + 1` `      ``if` `(i > ``0` `&& arr[i] == arr[i - ``1``] + ``1``)` `        ``count++;` `      `  `      ``// reset the count` `      ``else` `        ``count = ``1``;`   `      ``// update the maximum` `      ``ans = Math.max(ans, count);` `    ``}` `    ``return` `ans;` `  ``}`   `  ``// Driver code` `  ``public` `static` `void` `main (String[] args) {` `    ``int` `arr[ ] = { ``1``, ``9``, ``3``, ``4``, ``20``, ``2` `};` `    ``System.out.print(findLongestConseqSubarr(arr));` `  ``}` `}`   `// This code is contributed by hrithikgarg03188.`

## Python3

 `# python3 program to find longest` `# increasing consecutive subarray`   `# Returns length of the longest` `# consecutive subarray` `def` `findLongestConseqSubarr(v):`   `    ``ans, count ``=` `0``, ``0`   `    ``# find the maximum length` `    ``# by traversing the array` `    ``for` `i ``in` `range``(``0``, ``len``(v)):`   `        ``# Check if the current element` `        ``# is equal to previous element + 1` `        ``if` `(i > ``0` `and` `v[i] ``=``=` `v[i ``-` `1``] ``+` `1``):` `            ``count ``+``=` `1` `            `  `        ``# reset the count` `        ``else``:` `            ``count ``=` `1`   `        ``# update the maximum` `        ``ans ``=` `max``(ans, count)`   `    ``return` `ans`   `# Driver code` `if` `__name__ ``=``=` `"__main__"``:`   `    ``arr ``=` `[``1``, ``9``, ``3``, ``4``, ``20``, ``2``]` `    ``print``(findLongestConseqSubarr(arr))`   `    ``# This code is contributed by rakeshsahni`

## C#

 `// C# program for the above approach` `using` `System;` `class` `GFG` `{`   `  ``// Returns length of the longest` `  ``// consecutive subarray` `  ``static` `int` `findLongestConseqSubarr(``int``[] arr)` `  ``{` `    ``int` `ans = 0, count = 0;`   `    ``// find the maximum length` `    ``// by traversing the array` `    ``for` `(``int` `i = 0; i < arr.Length; i++)` `    ``{`   `      ``// Check if the current element ` `      ``// is equal to previous element + 1` `      ``if` `(i > 0 && arr[i] == arr[i - 1] + 1)` `        ``count++;`   `      ``// reset the count` `      ``else` `        ``count = 1;`   `      ``// update the maximum` `      ``ans = Math.Max(ans, count);` `    ``}` `    ``return` `ans;` `  ``}`   `  ``// Driver code` `  ``public` `static` `void` `Main()` `  ``{` `    ``int``[] arr = { 1, 9, 3, 4, 20, 2 };` `    ``Console.Write(findLongestConseqSubarr(arr));` `  ``}` `}`   `// This code is contributed by gfgking`

## Javascript

 ``

Output

`2`

Time Complexity: O(N)
Auxiliary Space: O(1)

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