信奥考前梳理4·二分

模板1

int l = 1, r = n;
while(l < r) {
	int mid = (l + r) / 2;
	if(check(mid)) {
		r = mid;
	}
	else {
		l = mid + 1;
	}
}

 

模板2

int l = 1, r = n;
while(l < r) {
	int mid = (l + r + 1) / 2;
	if(check(mid)) {
		l = mid;
	}
	else {
		r = mid - 1;
	}
}