Rotate an array by k positions in C (reversal method) Solution, output & explanation

#include <stdio.h>

static void reverse(int *a, int i, int j) {
    while (i < j) {
        int t = a[i];
        a[i++] = a[j];
        a[j--] = t;
    }
}

void rotate_left(int *a, int n, int k) {
    k %= n;
    reverse(a, 0, k - 1);       /* reverse the first k */
    reverse(a, k, n - 1);       /* reverse the rest */
    reverse(a, 0, n - 1);       /* reverse everything */
}

int main(void) {
    int a[] = {1, 2, 3, 4, 5, 6, 7};
    rotate_left(a, 7, 3);
    for (int i = 0; i < 7; i++)
        printf("%d ", a[i]);
    printf("\n");
    return 0;
}

4 5 6 7 1 2 3