# Longest increasing subarray

Given an array containing n numbers. The problem is to find the length of the longest contiguous subarray such that every element in the subarray is strictly greater than its previous element in the same subarray. Time Complexity should be O(n).

Examples:

```Input : arr[] = {5, 6, 3, 5, 7, 8, 9, 1, 2}
Output : 5
The subarray is {3, 5, 7, 8, 9}

Input : arr[] = {12, 13, 1, 5, 4, 7, 8, 10, 10, 11}
Output : 4
The subarray is {4, 7, 8, 10}
```

## Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

Algorithm:

```lenOfLongIncSubArr(arr, n)
Declare max = 1, len = 1
for i = 1 to n-1
if arr[i] > arr[i-1]
len++
else
if max < len
max = len
len = 1
if max < len
max = len
return max
```

## C++

 `// C++ implementation to find the length of  ` `// longest increasing contiguous subarray ` `#include ` ` `  `using` `namespace` `std; ` ` `  `// function to find the length of longest increasing  ` `// contiguous subarray ` `int` `lenOfLongIncSubArr(``int` `arr[], ``int` `n) ` `{ ` `    ``// 'max' to store the length of longest ` `    ``// increasing subarray ` `    ``// 'len' to store the lengths of longest ` `    ``// increasing subarray at diiferent  ` `    ``// instants of time ` `    ``int` `max = 1, len = 1; ` `     `  `    ``// traverse the array from the 2nd element ` `    ``for` `(``int` `i=1; i arr[i-1]) ` `            ``len++; ` `        ``else` `        ``{ ` `            ``// check if 'max' length is less than the length ` `            ``// of the current increasing subarray. If true,  ` `            ``// then update 'max' ` `            ``if` `(max < len)     ` `                ``max = len; ` `                 `  `            ``// reset 'len' to 1 as from this element ` `            ``// again the length of the new increasing ` `            ``// subarray is being calculated     ` `            ``len = 1;     ` `        ``}     ` `    ``} ` `     `  `    ``// comparing the length of the last ` `    ``// increasing subarray with 'max' ` `    ``if` `(max < len) ` `        ``max = len; ` `     `  `    ``// required maximum length ` `    ``return` `max; ` `} ` ` `  `// Driver program to test above ` `int` `main() ` `{ ` `    ``int` `arr[] = {5, 6, 3, 5, 7, 8, 9, 1, 2}; ` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr); ` `    ``cout << ``"Length = "` `         ``<< lenOfLongIncSubArr(arr, n); ` `    ``return` `0;      ` `} `

## Java

 `// JAVA Code to find length of  ` `// Longest increasing subarray ` `import` `java.util.*; ` ` `  `class` `GFG { ` `     `  `    ``// function to find the length of longest ` `    ``// increasing contiguous subarray ` `    ``public` `static` `int` `lenOfLongIncSubArr(``int` `arr[], ` `                                            ``int` `n) ` `    ``{ ` `        ``// 'max' to store the length of longest ` `        ``// increasing subarray ` `        ``// 'len' to store the lengths of longest ` `        ``// increasing subarray at diiferent  ` `        ``// instants of time ` `        ``int` `max = ``1``, len = ``1``; ` `          `  `        ``// traverse the array from the 2nd element ` `        ``for` `(``int` `i=``1``; i arr[i-``1``]) ` `                ``len++; ` `            ``else` `            ``{ ` `                ``// check if 'max' length is less  ` `                ``// than the length of the current  ` `                ``// increasing subarray. If true, ` `                ``// than update 'max' ` `                ``if` `(max < len)     ` `                    ``max = len; ` `                      `  `                ``// reset 'len' to 1 as from this  ` `                ``// element again the length of the  ` `                ``// new increasing subarray is being  ` `                ``// calculated     ` `                ``len = ``1``;     ` `            ``}     ` `        ``} ` `          `  `        ``// comparing the length of the last ` `        ``// increasing subarray with 'max' ` `        ``if` `(max < len) ` `            ``max = len; ` `          `  `        ``// required maximum length ` `        ``return` `max; ` `    ``} ` `     `  `    ``/* Driver program to test above function */` `    ``public` `static` `void` `main(String[] args)  ` `    ``{ ` `         ``int` `arr[] = {``5``, ``6``, ``3``, ``5``, ``7``, ``8``, ``9``, ``1``, ``2``}; ` `            ``int` `n = arr.length; ` `            ``System.out.println(``"Length = "` `+ ` `                      ``lenOfLongIncSubArr(arr, n)); ` `         `  `        ``} ` `    ``} ` `   `  `// This code is contributed by Arnav Kr. Mandal. `

## Python3

 `# Python 3 implementation to find the length of  ` `# longest increasing contiguous subarray ` ` `  `  `  `# function to find the length of longest  ` `# increasing contiguous subarray ` `def` `lenOfLongIncSubArr(arr, n) : ` ` `  `    ``# 'max' to store the length of longest ` `    ``# increasing subarray ` `    ``# 'len' to store the lengths of longest ` `    ``# increasing subarray at diiferent  ` `    ``# instants of time ` `    ``m ``=` `1`  `    ``l ``=` `1`  `      `  `    ``# traverse the array from the 2nd element ` `    ``for` `i ``in` `range``(``1``, n) : ` ` `  `        ``# if current element if greater than previous ` `        ``# element, then this element helps in building ` `        ``# up the previous increasing subarray encountered ` `        ``# so far ` `        ``if` `(arr[i] > arr[i``-``1``]) : ` `            ``l ``=``l ``+` `1`  `        ``else` `: ` ` `  `            ``# check if 'max' length is less than the length ` `            ``# of the current increasing subarray. If true,  ` `            ``# then update 'max' ` `            ``if` `(m < l)  : ` `                ``m ``=` `l  ` ` `  `            ``# reset 'len' to 1 as from this element ` `            ``# again the length of the new increasing ` `            ``# subarray is being calculated     ` `            ``l ``=` `1`  `         `  `         `  `    ``# comparing the length of the last ` `    ``# increasing subarray with 'max' ` `    ``if` `(m < l) : ` `        ``m ``=` `l ` `      `  `    ``# required maximum length ` `    ``return` `m ` ` `  `# Driver program to test above ` ` `  `arr ``=` `[``5``, ``6``, ``3``, ``5``, ``7``, ``8``, ``9``, ``1``, ``2``] ` `n ``=` `len``(arr) ` `print``(``"Length = "``, lenOfLongIncSubArr(arr, n)) ` ` `  ` `  `# This code is contributed ` `# by Nikita Tiwari. `

## C#

 `// C# Code to find length of ` `// Longest increasing subarray ` `using` `System; ` ` `  `class` `GFG { ` ` `  `    ``// function to find the length of longest ` `    ``// increasing contiguous subarray ` `    ``public` `static` `int` `lenOfLongIncSubArr(``int``[] arr, ` `                                             ``int` `n) ` `    ``{ ` `        ``// 'max' to store the length of longest ` `        ``// increasing subarray ` `        ``// 'len' to store the lengths of longest ` `        ``// increasing subarray at diiferent ` `        ``// instants of time ` `        ``int` `max = 1, len = 1; ` ` `  `        ``// traverse the array from the 2nd element ` `        ``for` `(``int` `i = 1; i < n; i++) { ` `             `  `            ``// if current element if greater than ` `            ``// previous element, then this element ` `            ``// helps in building up the previous ` `            ``// increasing subarray encountered ` `            ``// so far ` `            ``if` `(arr[i] > arr[i - 1]) ` `                ``len++; ` `            ``else` `{ ` `                 `  `                ``// check if 'max' length is less ` `                ``// than the length of the current ` `                ``// increasing subarray. If true, ` `                ``// than update 'max' ` `                ``if` `(max < len) ` `                    ``max = len; ` ` `  `                ``// reset 'len' to 1 as from this ` `                ``// element again the length of the ` `                ``// new increasing subarray is being ` `                ``// calculated ` `                ``len = 1; ` `            ``} ` `        ``} ` ` `  `        ``// comparing the length of the last ` `        ``// increasing subarray with 'max' ` `        ``if` `(max < len) ` `            ``max = len; ` ` `  `        ``// required maximum length ` `        ``return` `max; ` `    ``} ` ` `  `    ``/* Driver program to test above function */` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``int``[] arr = { 5, 6, 3, 5, 7, 8, 9, 1, 2 }; ` `        ``int` `n = arr.Length; ` `        ``Console.WriteLine(``"Length = "` `+  ` `                           ``lenOfLongIncSubArr(arr, n)); ` `    ``} ` `} ` ` `  `// This code is contributed by Sam007 `

## PHP

 ` ``\$arr``[``\$i``-1]) ` `            ``\$len``++; ` `        ``else` `        ``{ ` `             `  `            ``// check if 'max' length is ` `            ``// less than the length ` `            ``// of the current increasing ` `            ``// subarray. If true,  ` `            ``// then update 'max' ` `            ``if` `(``\$max` `< ``\$len``)  ` `                ``\$max` `= ``\$len``; ` `                 `  `            ``// reset 'len' to 1 as ` `            ``// from this element ` `            ``// again the length of  ` `            ``// the new increasing ` `            ``// subarray is being ` `            ``// calculated  ` `            ``\$len` `= 1;  ` `        ``}  ` `    ``} ` `     `  `    ``// comparing the length of the last ` `    ``// increasing subarray with 'max' ` `    ``if` `(``\$max` `< ``\$len``) ` `        ``\$max` `= ``\$len``; ` `     `  `    ``// required maximum length ` `    ``return` `\$max``; ` `} ` ` `  `    ``// Driver Code ` `    ``\$arr` `= ``array``(5, 6, 3, 5, 7, 8, 9, 1, 2); ` `    ``\$n` `= sizeof(``\$arr``); ` `    ``echo` `"Length = "``, lenOfLongIncSubArr(``\$arr``, ``\$n``); ` `     `  `// This code is contributed by nitin mittal. ` `?> `

Output:

```Length = 5
```

Time Complexity: O(n)

How to print the subarray?
We can print the subarray by keeping track of index with largest length.

## C++

 `// C++ implementation to find the length of  ` `// longest increasing contiguous subarray ` `#include ` `using` `namespace` `std; ` ` `  `// function to find the length of longest increasing  ` `// contiguous subarray ` `void` `printLogestIncSubArr(``int` `arr[], ``int` `n) ` `{ ` `    ``// 'max' to store the length of longest ` `    ``// increasing subarray ` `    ``// 'len' to store the lengths of longest ` `    ``// increasing subarray at diiferent  ` `    ``// instants of time ` `    ``int` `max = 1, len = 1, maxIndex = 0; ` `     `  `    ``// traverse the array from the 2nd element ` `    ``for` `(``int` `i=1; i arr[i-1]) ` `            ``len++; ` `        ``else` `        ``{ ` `            ``// check if 'max' length is less than the length ` `            ``// of the current increasing subarray. If true,  ` `            ``// then update 'max' ` `            ``if` `(max < len)     ` `            ``{ ` `                ``max = len; ` `                 `  `                ``// index assign the starting index of  ` `                ``// longest increasing contiguous subarray.    ` `                ``maxIndex = i - max; ` `            ``} ` `                 `  `            ``// reset 'len' to 1 as from this element ` `            ``// again the length of the new increasing ` `            ``// subarray is being calculated     ` `            ``len = 1;     ` `        ``}     ` `    ``} ` `     `  `    ``// comparing the length of the last ` `    ``// increasing subarray with 'max' ` `    ``if` `(max < len) ` `    ``{  ` `        ``max = len; ` `        ``maxIndex = n - max; ` `    ``} ` ` `  `    ``// Print the elements of longest increasing ` `    ``// contiguous subarray.  ` `    ``for` `(``int` `i=maxIndex; i

## Java

 `// JAVA Code For Longest increasing subarray ` `import` `java.util.*; ` ` `  `class` `GFG { ` `     `  `    ``// function to find the length of longest  ` `    ``// increasing contiguous subarray ` `    ``public` `static` `void` `printLogestIncSubArr(``int` `arr[],  ` `                                              ``int` `n) ` `    ``{ ` `        ``// 'max' to store the length of longest ` `        ``// increasing subarray ` `        ``// 'len' to store the lengths of longest ` `        ``// increasing subarray at diiferent  ` `        ``// instants of time ` `        ``int` `max = ``1``, len = ``1``, maxIndex = ``0``; ` `          `  `        ``// traverse the array from the 2nd element ` `        ``for` `(``int` `i = ``1``; i < n; i++) ` `        ``{ ` `            ``// if current element if greater than  ` `            ``// previous element, then this element  ` `            ``// helps in building up the previous  ` `            ``// increasing subarray encountered ` `            ``// so far ` `            ``if` `(arr[i] > arr[i-``1``]) ` `                ``len++; ` `            ``else` `            ``{ ` `                ``// check if 'max' length is less ` `                ``// than the length of the current ` `                ``// increasing subarray. If true,  ` `                ``// then update 'max' ` `                ``if` `(max < len)     ` `                ``{ ` `                    ``max = len; ` `                      `  `                    ``// index assign the starting  ` `                    ``// index of longest increasing ` `                    ``// contiguous subarray.    ` `                    ``maxIndex = i - max; ` `                ``} ` `                      `  `                ``// reset 'len' to 1 as from this ` `                ``// element again the length of the ` `                ``// new increasing subarray is  ` `                ``// being calculated     ` `                ``len = ``1``;     ` `            ``}     ` `        ``} ` `          `  `        ``// comparing the length of the last ` `        ``// increasing subarray with 'max' ` `        ``if` `(max < len) ` `        ``{  ` `            ``max = len; ` `            ``maxIndex = n - max; ` `        ``} ` `      `  `        ``// Print the elements of longest  ` `        ``// increasing contiguous subarray.  ` `        ``for` `(``int` `i = maxIndex; i < max+maxIndex; i++) ` `            ``System.out.print(arr[i] + ``" "``); ` `    ``} ` `     `  `    ``/* Driver program to test above function */` `    ``public` `static` `void` `main(String[] args)  ` `    ``{ ` `        ``int` `arr[] = {``5``, ``6``, ``3``, ``5``, ``7``, ``8``, ``9``, ``1``, ``2``}; ` `        ``int` `n = arr.length; ` `        ``printLogestIncSubArr(arr, n); ` `         `  `    ``} ` `} ` `   `  `// This code is contributed by Arnav Kr. Mandal. `

## Python3

 `# Python 3 implementation to find the length of  ` `# longest increasing contiguous subarray ` ` `  ` `  `# function to find the length of longest increasing  ` `# contiguous subarray ` `def` `printLogestIncSubArr( arr, n) : ` ` `  `    ``# 'max' to store the length of longest ` `    ``# increasing subarray ` `    ``# 'len' to store the lengths of longest ` `    ``# increasing subarray at diiferent  ` `    ``# instants of time ` `    ``m ``=` `1` `    ``l ``=` `1` `    ``maxIndex ``=` `0` `      `  `    ``# traverse the array from the 2nd element ` `    ``for` `i ``in` `range``(``1``, n) : ` ` `  `        ``# if current element if greater than previous ` `        ``# element, then this element helps in building ` `        ``# up the previous increasing subarray  ` `        ``# encountered so far ` `        ``if` `(arr[i] > arr[i``-``1``]) : ` `            ``l ``=``l ``+` `1` `        ``else` `: ` ` `  `            ``# check if 'max' length is less than the length ` `            ``# of the current increasing subarray. If true,  ` `            ``# then update 'max' ` `            ``if` `(m < l)  : ` `                ``m ``=` `l  ` ` `  `                ``# index assign the starting index of  ` `                ``# longest increasing contiguous subarray.    ` `                ``maxIndex ``=` `i ``-` `m ` `                   `  `            ``# reset 'len' to 1 as from this element ` `            ``# again the length of the new increasing ` `            ``# subarray is being calculated     ` `            ``l ``=` `1`     `         `  `         `  `    ``# comparing the length of the last ` `    ``# increasing subarray with 'max' ` `    ``if` `(m < l) : ` `        ``m ``=` `l ` `        ``maxIndex ``=` `n ``-` `m ` `     `  `    ``# Print the elements of longest ` `    ``# increasing contiguous subarray.  ` `    ``for` `i ``in` `range``(maxIndex, (m``+``maxIndex)) : ` `        ``print``(arr[i] , end``=``" "``) ` `         `  `# Driver program to test above ` `arr ``=` `[``5``, ``6``, ``3``, ``5``, ``7``, ``8``, ``9``, ``1``, ``2``] ` `n ``=` `len``(arr) ` `printLogestIncSubArr(arr, n) ` `     `  `     `  `# This code is contributed ` `# by Nikita Tiwari `

## C#

 `// C# Code to print  ` `// Longest increasing subarray ` `using` `System; ` ` `  `class` `GFG { ` ` `  `    ``// function to find the length of longest ` `    ``// increasing contiguous subarray ` `    ``public` `static` `void` `printLogestIncSubArr(``int``[] arr, ` `                                                ``int` `n) ` `    ``{ ` `        ``// 'max' to store the length of longest ` `        ``// increasing subarray ` `        ``// 'len' to store the lengths of longest ` `        ``// increasing subarray at diiferent ` `        ``// instants of time ` `        ``int` `max = 1, len = 1, maxIndex = 0; ` ` `  `        ``// traverse the array from the 2nd element ` `        ``for` `(``int` `i = 1; i < n; i++) { ` `             `  `            ``// if current element if greater than ` `            ``// previous element, then this element ` `            ``// helps in building up the previous ` `            ``// increasing subarray encountered ` `            ``// so far ` `            ``if` `(arr[i] > arr[i - 1]) ` `                ``len++; ` `            ``else`  `            ``{ ` `                ``// check if 'max' length is less ` `                ``// than the length of the current ` `                ``// increasing subarray. If true, ` `                ``// then update 'max' ` `                ``if` `(max < len) { ` `                    ``max = len; ` ` `  `                    ``// index assign the starting ` `                    ``// index of longest increasing ` `                    ``// contiguous subarray. ` `                    ``maxIndex = i - max; ` `                ``} ` ` `  `                ``// reset 'len' to 1 as from this ` `                ``// element again the length of the ` `                ``// new increasing subarray is ` `                ``// being calculated ` `                ``len = 1; ` `            ``} ` `        ``} ` ` `  `        ``// comparing the length of the last ` `        ``// increasing subarray with 'max' ` `        ``if` `(max < len) { ` `            ``max = len; ` `            ``maxIndex = n - max; ` `        ``} ` ` `  `        ``// Print the elements of longest ` `        ``// increasing contiguous subarray. ` `        ``for` `(``int` `i = maxIndex; i < max + maxIndex; i++) ` `            ``Console.Write(arr[i] + ``" "``); ` `    ``} ` ` `  `    ``/* Driver program to test above function */` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``int``[] arr = { 5, 6, 3, 5, 7, 8, 9, 1, 2 }; ` `        ``int` `n = arr.Length; ` `        ``printLogestIncSubArr(arr, n); ` `    ``} ` `} ` ` `  `// This code is contributed by Sam007 `

## PHP

 ` ``\$arr``[``\$i` `- 1]) ` `            ``\$len``++; ` `        ``else` `        ``{ ` `            ``// check if 'max' length is less  ` `            ``// than the length of the current  ` `            ``// increasing subarray. If true,  ` `            ``// then update 'max' ` `            ``if` `(``\$max` `< ``\$len``)  ` `            ``{ ` `                ``\$max` `= ``\$len``; ` `                 `  `                ``// index assign the starting  ` `                ``// index of longest increasing ` `                ``// contiguous subarray.  ` `                ``\$maxIndex` `= ``\$i` `- ``\$max``; ` `            ``} ` `                 `  `            ``// reset 'len' to 1 as from this ` `            ``// element again the length of  ` `            ``// the new increasing subarray ` `            ``// is being calculated  ` `            ``\$len` `= 1;  ` `        ``}  ` `    ``} ` `     `  `    ``// comparing the length of ` `    ``// the last increasing  ` `    ``// subarray with 'max' ` `    ``if` `(``\$max` `< ``\$len``) ` `    ``{  ` `        ``\$max` `= ``\$len``; ` `        ``\$maxIndex` `= ``\$n` `- ``\$max``; ` `    ``} ` ` `  `    ``// Print the elements of ` `    ``// longest increasing ` `    ``// contiguous subarray.  ` `    ``for` `(``\$i` `= ``\$maxIndex``;  ` `         ``\$i` `< (``\$max` `+ ``\$maxIndex``); ``\$i``++) ` `        ``echo``(``\$arr``[``\$i``] . ``" "``) ; ` `         `  `} ` ` `  `// Driver Code ` `\$arr` `= ``array``(5, 6, 3, 5, 7,  ` `             ``8, 9, 1, 2); ` `\$n` `= sizeof(``\$arr``); ` `printLogestIncSubArr(``\$arr``, ``\$n``); ` `     `  `// This code is contributed ` `// by Shivi_Aggarwal ` `?> `

Output:

```3 5 7 8 9
```

This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.