NO7——二分

 int binsearch(int *t,int k,int n)
 {//t为数组，k是要查找的数，n为长度，此为升序
     int low = ,high = n,mid;
     while(low<=high)
     {
         mid = (low+high)/;
         if(k == t[mid])
         return mid;
         else if(k<t[mid])
         high = mid-;
         else
         low = mid+;
     }
     return -;
 }