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

 1 #include <iostream>
 2 #include <unordered_map>
 3 using namespace std;
 4 int N, num[100001];
 5 int main()
 6 {
 7     cin >> N;
 8     unordered_map<int, int> numbers;
 9     for (int i = 0; i < N; ++i)
10     {
11         cin >> num[i];
12         numbers[num[i]]++;//为了保证单得到存数的位子顺序，借助num[i]
13     }
14     for (int i = 0; i < N; ++i)
15     {
16         if (numbers[num[i]] == 1)
17         {
18             cout << num[i] << endl;
19             return 0;
20         }
21     }
22     cout << "None" << endl;
23     return 0;
24 }