PTA(Advanced Level)1041.Be Unique

Being unique is so important to people on Mars that even their lottery is designed in a unique way. The rule of winning is simple: one bets on a number chosen from [1,104]. The first one who bets on a unique number wins. For example, if there are 7 people betting on { 5 31 5 88 67 88 17 }, then the second one who bets on 31 wins.

Input Specification:

Each input file contains one test case. Each case contains a line which begins with a positive integer N (≤105) and then followed by N bets. The numbers are separated by a space.

Output Specification:

For each test case, print the winning number in a line. If there is no winner, print None instead.

Sample Input 1:

7 5 31 5 88 67 88 17

Sample Output 1:

31

Sample Input 2:

5 888 666 666 888 888

Sample Output 2:

None

思路

• 用map容器记录字符出现的次数，同时另开一个数组record记录输入的顺序
• 读完之后扫描record，依次判断是否是unique的

代码

#include<bits/stdc++.h>
using namespace std;
int record[10010];
int len = 0;
int main()
{
	int n;
	scanf("%d", &n);

	int t;
	map<int,int> mp;
	for(int i=0;i<n;i++)
	{
		scanf("%d", &t);
		if(mp.count(t) == 0)     //判断是否之前有出现过
		{
			record[len++] = t;  //记录读进来的顺序
			mp[t] = 1;
		}else mp[t]++;    //否则出现次数+1
	}
	for(int i=0;i<len;i++)
	{
		if(mp[record[i]] == 1)
		{
			printf("%d\n", record[i]);
			return 0;
		}
	}
	printf("None\n");
	return 0;
}

引用

https://pintia.cn/problem-sets/994805342720868352/problems/994805444361437184