二分查找

 1 int bin_search(ElementType a[], int num,ElementType obj)
 2 {
 3     int low=0,high=num-1,mid;
 4     while(low<=high)
 5     {
 6         mid=(low+high)/2;
 7         if(a[mid]==obj)
 8         {
 9             return mid;
10         }
11         else if(a[mid]<obj)
12         {
13             low=mid+1;
14         }
15         else
16         {
17             high=mid-1;
18         }
19     }
20     return -1;
21 }

int bin_search(ElementType a[], int left,int right,ElementType obj)
{
    int low=left,high=right,mid;
    while(low<=high)
    {
        mid=(low+high)/2;
        if(a[mid]==obj)
        {
            return mid;
        }
        else if(a[mid]<obj)
        {
            low=mid+1;
        }
        else
        {
            high=mid-1;
        }
    }
    return -1;
}