学步园

int bfind(int* a,int len,int val)
{
    int m = len/2;
    int l = 0;
    int r = len;
    while(l!=m && r!= m)
    {
        if(a[m] > val)
        {
            r = m;
            m = (m+l)/2;
        }
        else if(a[m] < val)
        {
            l = m;
            m = (m+r)/2;
        }
        else
            return m;
    }
    return -1;   //没有找到
}