Sliding window_basic

// Given an array of integers Arr of size N and a number K. Return the maximum sum of a subarray of size K.
// code in c++

int maximumSumSubarray(int K, vector<int> &A , int N){
    int i = 0; // starting point of window
    int maxi = 0, s = 0;
    
    for(int j = 0; j < N; j++){
        s += A[j];
        if(j - i + 1 == K){ // when length of subarray becomes equal to K
            maxi = max(maxi, s);
            s -= A[i];
            i += 1;
        }
    }
    
    return maxi;
}


// Sliding window technique is useful for solving problems in array or string, especially it is considered as a technique that could reduce the time complexity from O(n²) to O(n).