C 二分查找

void fid( a[] , i ) //传入一个数组与其长度
{
int left=0,right=i;

while(right-left>1)
{
if( mid < a[((left+right)/2)] )
right = ((left+right)/2);

    if ( mid > a[((left+right)/2)] )        left = ((left+right)/2);    if ( mid == a[((left+right)/2)])    {        printf("%d\n",((left+right)/2));        break;    }}   

}