7-2

7-2.c

#include <stdio.h>

void swap_array (int a[], int i, int j) {
    int t = a[i];

    a[i] = a[j];
    a[j] = t;
}

int main () {
    int i;
    int a[] = {0, 1, 2, 3, 4, 5, 6};

    swap_array(a, 3, 4);

    for (i=0; i<sizeof(a)/sizeof(a[0]); i++)
        printf("%d\n", a[i]);

    return 0;
}