2420. Find All Good Indices

You are given a 0-indexed integer array nums of size n and a positive integer k.

We call an index i in the range k <= i < n - k good if the following conditions are satisfied:

• The k elements that are just before the index i are in non-increasing order.
• The k elements that are just after the index i are in non-decreasing order.

Return an array of all good indices sorted in increasing order.

class Solution {
public:
    vector<int> goodIndices(vector<int>& A, int k) {
        int n = A.size();
        vector<int> inc(n,1), dec(n,1);
        for(int i = 1; i < n; i++) if(A[i-1] >= A[i]) dec[i] = dec[i-1] + 1;
        for(int i = n - 2; i >= 0; i--) if(A[i+1] >= A[i]) inc[i] = inc[i+1] + 1;
        vector<int> res;
        for(int i = k; i < n - k; i++) if(inc[i+1] >= k and dec[i-1] >= k) res.push_back(i);
        return res;
    }
};