题目描述

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 [1,10^​4​​ ]. 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 (≤10^​5​​ ) 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

代码

#include <iostream>
#include <vector>
using namespace std;
int book[10001];
int main() {
    int n, flag = 0;
    scanf("%d", &n);
    vector<int> b(n);
    for (int i = 0; i < n; i++) {
        cin >> b[i];
        book[b[i]]++;
    }
    for (int i = 0; i < n; i++) {
        if (book[b[i]] == 1) {
            printf("%d", b[i]);
            return 0;
        }
    }
    printf("None");
    return 0;
}