Nice Array

Problem Statement - link #

You are given an array arr of n integers. An array is nice if for each index i, the value of arr[i] = i. Your task is to find the length of the longest subarray of the array arr which is nice. Consider 1-based indexing.

Your Task:

You don’t need to read input or print anything. Your task is to complete the function niceSubarray() which takes an integer n, and an array arr[] as input parameters and returns the length of the longest nice subarray.

Expected Time Complexity: O(n)
Expected Auxiliary Space: O(1)

Examples #

Example 1:

Input:
n = 7
arr = {2,1,2,3,1,2,2}
Output:
3
Explanation:
The subarray {1,2,3} is the longest nice subarray.

Example 2:

Input:
n = 4
arr = {3,5,2,6}
Output:
0
Explanation:
There is no nice subarray.

Constraints #

• 1 ≤ N <= 10^5
• 1 ≤ arr[i] ≤ 10^5

Solutions #

class Solution{
  public:
    int niceSubarray(int n, vector<int> &arr) {
        // code here
        int res = 0, cur = 0;
        for(int i = 0; i < n; i++) {
            cur = i;
            while(cur < n && arr[cur] == cur - i + 1) {
                cur++;
            
            }
            res = max(res, cur - i);
        }
        return res;
    }
};