1041 Be Unique (20 分)

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

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:

Sample Input 2:

5 888 666 666 888 888

Sample Output 2:

None

题解：

用一个flag数组存储每个数字出现的次数，输出第一个次数为1的那一位，没有则输出None

注意：两层for循环会运行超时！

#include<bits/stdc++.h>
using namespace std;
const int maxn=100010;

int main(){
    vector<int> v;
    int flag[maxn];
    fill(flag,flag+maxn,0);
    int n,m;
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        scanf("%d",&m);
        v.push_back(m);
        flag[m]++;
    }
    for(int i=0;i<v.size();i++){
        if(flag[v[i]]==1){
            printf("%d
",v[i]);
            return 0;
        }
    }
    printf("None
");
    return 0;
}