/*要使用二分查找，必须数组已经按照从大到小的顺序排好*/
#include <stdio.h>
int find(int a[],int t)
{
 int left=0,mid,right=14;
 while(1)
 {
  mid=(left+right)/2;
  if (t=a[mid])
      return mid;
  else
  {
   if (t>a[mid])
        left=mid+1;
   else right=mid-1;     /*这里不能在else外面加大括号*/
  }
 }
 return -1;
}
main()
{
 int a[15]={3,7,12,19,21,24,26,33,39,41,45,50,52,64,68};
 printf("%d\n",find(a,52));

}