1041. Be Unique (20)

题目如下：

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

题目要求找出一个序列中第一个在序列中只出现了一次的数，实现方法很简单，使用map记录每个数出现的次数，然后使用vector记录输入顺序，依次判断即可。

#include <iostream>
#include <map>
#include <vector>
#include <stdio.h>

using namespace std;

int main()
{
    map<int,int> numMap;
    vector<int> nums;
    int N;
    cin >> N;
    int num;
    for(int i = 0; i < N; i++){
        scanf("%d",&num);
        numMap[num]++;
        nums.push_back(num);
    }
    num = - 1;
    for(int i = 0; i < nums.size(); i++){
        if(numMap[nums[i]] == 1){
            num = nums[i];
            break;
        }
    }
    if(num == -1) cout << "None" << endl;
    else cout << num << endl;

    return 0;
}