Codeforces Round 960 (Div. 2)

A. Submission Bait

Alice and Bob are playing a game in an array $a$ of size $n$.

They take turns to do operations, with Alice starting first. The player who can not operate will lose. At first, a variable $mx$ is set to $0$.

In one operation, a player can do:

• Choose an index $i$ ($1\le i\le n$) such that $a_i\ge mx$ and set $mx$ to $a_i$. Then, set $a_i$ to $0$.

Determine whether Alice has a winning strategy.

思路：排序之后从最大到最小只要个数是奇数Alice就能赢

反思：反思刚开始想到第一个是奇数能赢，后来想到了第一个偶数，第二个是奇数也能赢，很遗憾没想到不止最大的两个数

代码

#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
	int t;
	cin>>t;
	while(t--)
	{
		int n;
		cin>>n;
		int a[59];
		int b[59]={0};
		for(int i=1;i<=n;i++)
		{
			cin>>a[i];
			b[a[i]]++;//计算相同数字的个数
		}
		int f=0;
		sort(a+1,a+n+1);
		for(int i=n;i>=1;i--)
		{
			if(b[a[i]]%2!=0)//只要遇到奇数用f标志
			f=1; 
		}
		if(f%2!=0)
			cout<<"YES"<<'\n';
		else 
			cout<<"NO"<<'\n';
	}
    return 0;
}