我自己的模板

	int l=0,r=100,ans=0;
	while(l<=r)
	{
		mid=(l+r)/2;
		if (check(mid)) {l=mid+1;ans = mid; }else r=mid-1; //注意+1，-1否則死迴圈
	}

int main(){
    == key 
    int m;
    while ( l <= r ) {
        m = ( l + r ) >> 1;
        if ( x[m] == key ) return m;
        else if ( key > x[m] ) 
            l = m + 1;
        else
            r = m - 1; 
    }
    
    >= key 中最小的
    int ret;
    while ( l <= r ) {
        m = ( l + r ) >> 1;
        if ( x[m] >= key ) {
            ret = m;
            r = m - 1;  
        } else
            l = m + 1;
    }
    
    <= key 中最大的
    int ret;
    while ( l <= r ) {
        m = ( l + r ) >> 1;
        if ( x[m] <= key ) {
            ret = m;
            l = m + 1;  
        } else
            r = m - 1;
    }

}