B. Taxi1100 / 贪心

Posted 2021-11-11 幽殇默

https://codeforces.com/problemset/problem/158/B
1-3 2-2 2-1-1尽量多配对

#include<bits/stdc++.h>
using namespace std;
int a[10],n,x;
int main(void)
{
	cin>>n;
	for(int i=0;i<n;i++) cin>>x,a[x]++; 
	int ans=a[4];
	while(a[3]&&a[1]) ans++,a[3]--,a[1]--;
	if(a[3]>0) ans+=a[3];
	while(a[2]>0&&a[1]>0) ans++,a[2]--,a[1]-=2;
	if(a[2]>0) 
	{
		ans+=a[2]/2;
		if(a[2]%2)  ans++;
	}
	if(a[1]>0) 
	{
		ans+=a[1]/4;
		if(a[1]>0&&a[1]%4) ans++;
	}
	cout<<ans<<endl;
	return 0;
}