P1873 砍树

题目：

代码：

#include <bits/stdc++.h>
using namespace std;

const int N = 1000000 + 10;
int n, m, a[N];

bool cmp(int i1, int i2)
{
	return i1 > i2;
}

int main()
{
	cin >> n >> m;
	for (int i = 0; i < n; i++) cin >> a[i];
	sort(a, a + n, cmp);
	
	int l = 0, r = 400000;
	while (l < r)    //l = r的时候结束
	{
		int mid = (l + r + 1) / 2;
		long long total = 0;
		for (int i = 0; i < n; i++)
		{
			if (a[i] > mid) total += a[i] - mid;
			else break;
		}
		if (total > m) l = mid;    //初始l = 0
		else if (total < m) r = mid - 1;
		else
		{
			cout << mid; 	
			return 0;	
		}
	}
	cout << l;
	return 0;
}