二分模板（整数、浮点）

划分成[l, mid]和[mid + 1, r]

int bsearch_1(int l, int r)
{
    while (l < r)
    {
        int mid = l + r >> 1;
        if (check(mid)) r = mid;
        else l = mid + 1;
    }
    return l;
}

划分成[l, mid - 1]和[mid, r]时

int bsearch_2(int l, int r)
{
    while (l < r)
    {
        int mid = l + r + 1 >> 1;
        if (check(mid)) l = mid;
        else r = mid - 1;
    }
    return l;
}

浮点二分

double bsearch_3(double l,double r){
	while(r-l>1e-8){
		double mid = (l+r)/2.0;
		if(check(mid)) l=mid;
		else r=mid;
	}
	return l;
}