ArraySumTillK

Usage

    int[] arr = { 1, 2, 3, 4, 5, 6 };
    int k = 3;
    // {1,3,6,9,12,15};
    int[] result = calculateArraySumTillK(arr, k);
    for (int i : result) {
        System.out.print(i + " ");
    }

calculateArraySumTillK

int[] calculateArraySumTillK(int[] arr, int k) {
    int[] result = new int[arr.length];
    int prevSum = 0;
    for (int i = 0; i < arr.length; i++) {
        prevSum += arr[i];
        if (i >= k) {
            prevSum -= arr[i - k];
        }
        result[i] = prevSum;
    }
    return result;
}