Sliding Window Sum

Code

#include <stdio.h>

void return_single_line(int *arr, int n, char out[]) {
    int pos = 0; 
    for (int i = 0; i < n; i++) {
        pos += sprintf(out + pos, "%d", arr[i]);
        if (i < n - 1) {
            pos += sprintf(out + pos, " ");
        }
    }
}

void sliding_window_sum(int arr[], int n, int k, char out[]) {
    int num_windows = n - k + 1;
    int buff_sums[num_windows];

    for (int i = 0; i <= n - k; i++) {
        int sum = 0;
        for (int j = i; j < i + k; j++) {
            sum += arr[j];
        }
        buff_sums[i] = sum;
    }
    return_single_line(buff_sums, num_windows, out);
}


int main() {

    int n, k, arr[100];
    char buffer[100];

    scanf("%d %d", &n, &k);

    for (int i = 0; i < n; i++) scanf("%d", &arr[i]);
    sliding_window_sum(arr, n, k, buffer);
    printf("%s", buffer);
    return 0;

}

Solving Approach