常用算法

int  binary_search(int a[],int len,int goal)
{
    int beg = 0;
    int end = len - 1;
    while(beg <= end)
    {
        int middle = (end + beg + 1)/2;
        if(a[middle] == goal)
            return middle;
        if(a[middle] > goal)
            end = middle - 1;
        else
            beg = middle + 1;
    }
    return -1;
}