Reading an array and doing binary searches on it

/* binary.c - Binary search using two methods. The first is more intuitive, but it is
slower.
*/

#include <stdio.h>
#include <sys/time.h>

/* Given a sorted array with n elements, we search for who using binary search.
We return a position where found, or -1 if not there
*/
int binary1(int n, int a[n], int who) {
int left = 0; 
int right = n-1;
while (left <= right) {
int mid = left + (right-left)/2;
if (who < a[mid])
right = mid - 1;
else if (who > a[mid])
left = mid + 1;
else
return mid;
}
return -1;
}

/* Given a sorted array with n elements, we search for who using binary search.
We return a position where found, or -1 if not there
*/
int binary2(int n, int a[n], int who) {
int p = n/2;
while (n > 0) {
n = n/2;
if (who < a[p]) {
p -= n;
} else if (who > a[p]) {
p += n;
} else
return p;
}
return -1;
}

/* Returns the difference in microseconds between before and after */
long timediff(struct timeval before, struct timeval after) {
long sec = after.tv_sec - before.tv_sec;
long microsec = after.tv_usec - before.tv_usec;
return 1000000*sec + microsec;
}

int main() {
int a[] = {1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33};
int n = sizeof(a)/sizeof(int);
int where;
struct timeval before;
struct timeval after;
int k;
int j;
gettimeofday(&before, NULL);
for (j = 0; j < 1000000; j++)
for (k = 0; k < 2*n+1; k++) {
where = binary1(n, a, k);
// printf("who = %d, \tvalue = %d\n", k, where); 
}
gettimeofday(&after, NULL);
printf("before=[%ld,%ld], after=[%ld,%ld]\n", before.tv_sec, before.tv_usec,
after.tv_sec, after.tv_usec);
printf("The difference is %ld\n", timediff(before, after));
printf("---------------------------------------------\n");
gettimeofday(&before, NULL);
for (j = 0; j < 1000000; j++)
for (k = 0; k < 2*n+1; k++) {
where = binary2(n, a, k);
// printf("who = %d, \tvalue = %d\n", k, where); 
}
gettimeofday(&after, NULL);
printf("before=[%ld,%ld], after=[%ld,%ld]\n", before.tv_sec, before.tv_usec,
after.tv_sec, after.tv_usec);
printf("The difference is %ld\n", timediff(before, after));
return 0;
}