NO7——二分

 1 int binsearch(int *t,int k,int n)
 2 {//t为数组，k是要查找的数，n为长度，此为升序
 3     int low = 1,high = n,mid;
 4     while(low<=high)
 5     {
 6         mid = (low+high)/2;
 7         if(k == t[mid])
 8         return mid;
 9         else if(k<t[mid])
10         high = mid-1;
11         else
12         low = mid+1;
13     }
14     return -1;
15 }