2005. Lovely Number

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分类专栏：西西里水题（水到爆阿）刷题之旅文章标签： integer output numbers input each 网络

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本博客介绍了一个算法，用于找出在一个整数序列中出现奇数次的唯一数字，序列中的其他数字都出现偶数次。通过使用集合数据结构来解决此问题，该算法在效率上表现出色。

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2005. Lovely Number

Description

Every time after got a solution from kevin, ivan repeats again and again,"Are there any better ones?". It seems more worse this time. Given a sequence of numbers, which ivan is sure that all of them appear even times except only one "lovely number" appears odd times, kevin must find out the lovely number as soon as possible. So, let's rock!

Input

There are multiple test cases.

Each test case contains two lines. The first line is an integer N, 1 <= N <= 10001, and N % 2 = 1. The second line contains N integers, separated by spaces.

Input is terminated by EOF.

Output

For each test case, output a line of an integer, which should be the lovely number.

Sample Input

31 2 157 7 7 7 372 2 4 4 4 2 2

Sample Output

Problem Source

2010中山大学新手赛-网络预选赛 ivankevin@argo

#include <iostream>
#include <set>
using namespace std;

int main()
{
	int t;
	while(cin>>t)
	{
		int temp;
		set<int>myset;
		while(t--)
		{
			cin>>temp;
			if(myset.count(temp))
				myset.erase(temp);
			else
			    myset.insert(temp);
		}
		cout<<*myset.begin()<<endl;
	}
	return 0;
}