1041 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

题意：

　　找出一组数字中只出现一次的那个数字（第一个）。

思路：

　　简单模拟。

Code：

#include <bits/stdc++.h>

using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> v(n);
    map<int, int> mp;
    for (int i = 0; i < n; ++i) {
        cin >> v[i];
        mp[v[i]]++;
    }
    int ans = -1;
    for (int i = 0; i < n; ++i) {
        if (mp[v[i]] == 1) {
            ans = v[i];
            break;
        }
    }
    if (ans > 0)
        cout << ans << endl;
    else
        cout << "None" << endl;
    return 0;
}