二分查找C语言实现

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define N 20
#define N_RAND 200
int cmp( const void *a , const void *b ){
return *(int *)a > *(int *)b ? 1 : -1;
}

//返回在数组中位置
int B_Search(int *a, int p, int q, int key){
while(p<=q){
int r=(p+q)/2;
if(a[r]==key) return r;
else if(a[r] > key) q=r-1;
else p=r+1;
}
return -1;
}

int main(){
int i, a
;
srand((unsigned)time(NULL));
for(i=0;i<N;i++){
a[i]=rand()%N_RAND;
printf("%d ",a[i]);
}
printf("\n");
qsort(a,N,sizeof(int),cmp);
for(i=0;i<N;i++){
printf("%d ",a[i]);
}
printf("\n");
for(i=0;i<N;i++){
printf("元素位置为%d \n",B_Search(a,0,N-1,a[i]));
}
system("pause");
return 0;
}