codeforces 839 B Game of the Rows

题目链接：http://codeforces.com/contest/839/problem/B

#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int maxn = 100 + 5;

int n, k;
int a[maxn];

void display(int n){
	for (int i = 0; i < n; ++i){
		printf("(%d)%d ", i + 1, a[i]);
	}
	printf("\n");
}

int main(){
	scanf("%d%d", &n, &k);
	for (int i = 0; i < k; ++i){
		scanf("%d", a + i);
	}
	int four = n, two = 2 * n, one;
	int t;
	//先往3,4,5,6安排士兵
	for (int i = 0; i < k; ++i){
		t = min(a[i] / 4, four);
		four -= t;
		a[i] -= t * 4;
		if (four == 0){
			break;
		}
	}
	//把剩余的四连座分解为一个双座和一个单座
	two += four;
	one = four;
	four = 0;
	//再往1,2  7,8上安排士兵
	for (int i = 0; i < k; ++i){
		t = min(a[i] / 2, two);
		two -= t;
		a[i] -= t * 2;
		if (two == 0){
			break;
		}
	}
	int s = 0;
	//统计剩余士兵数量（每个group最多还剩一名士兵）
	for (int i = 0; i < k; ++i){
		s += a[i];
	}
	//单人座和双人座都还能坐一个士兵，若无法坐下全部士兵，则没有满足题意的策略
	bool status = (s <= (two + one));
	printf("%s\n", status ? "YES": "NO");
	return 0;
}