7-2.c

#include <stdio.h>

void swap_array(int a[], int x, int y)
{
	int t = a[x];

	a[x] = a[y];
	a[y] = 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;
}