《算法笔记》4.2小节——算法初步-＞哈希问题 C: Be Unique (20)

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博客围绕火星独特的彩票规则展开，规则是从[1, 104]选号，首个选到唯一数字者获胜。给出了问题描述、输入输出要求及样例，需根据输入的投注数字找出获胜数字，若无则输出“None”。

问题 C: Be Unique (20)

时间限制 : 1.000 sec 内存限制 : 32 MB

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, 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.

输入

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.

输出

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

样例输入

7 5 31 5 88 67 88 17
5 888 666 666 888 888

样例输出

31
None

#include <iostream>
#include <set>


using namespace std;
int a[100005];

int main() {
    int m;
    while (cin >> m) {
        bool flag = false;
        multiset<int> set;
        for (int i = 0; i < m; ++i) {
            cin >> a[i];
            set.insert(a[i]);
        }
        for (int i = 0; i < m; i++) {
            if (set.count(a[i]) == 1) {
                cout << a[i] << endl, flag = true;
                break;
            }
        }
        if (!flag)
            cout << "None" << endl;
    }
    return 0;
}