PAT甲级——A1041 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]. 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 (≤) 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

#include <iostream>
#include <unordered_map>
using namespace std;
int N, num[100001];
int main()
{
    cin >> N;
    unordered_map<int, int> numbers;
    for (int i = 0; i < N; ++i)
    {
        cin >> num[i];
        numbers[num[i]]++;//为了保证单得到存数的位子顺序，借助num[i]
    }
    for (int i = 0; i < N; ++i)
    {
        if (numbers[num[i]] == 1)
        {
            cout << num[i] << endl;
            return 0;
        }
    }
    cout << "None" << endl;
    return 0;
}