1041BeUnique

1041 Be Unique

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0、题目

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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.

Input Specification:

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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.

Output Specification:

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

Sample Input 1:

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7 5 31 5 88 67 88 17

Sample Output 1:

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31

Sample Input 2:

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5 888 666 666 888 888

Sample Output 2:

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None

1、大致题意

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给n个数字，按照读入顺序，哪个数字是第一个在所有数字中只出现一次的数字。如果所有数字出现都超过了一次，则输出None

2、基本思路

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简单题。

建立一个数组，存储每个数字出现的次数，然后遍历一遍输入的顺序看是否有出现次数为1的数字

3、AC代码

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#include <cstdio>
using namespace std;
int a[100001], m[100000];
int main() {
    int n;
    scanf("%d", &n);
    for(int i = 0; i < n; i++) {
        scanf("%d", &a[i]);
        m[a[i]]++;
    }
    for(int i = 0; i < n; i++) {
        if(m[a[i]] == 1) {
            printf("%d", a[i]);
            return 0;
        }
    }
    printf("None");
    return 0;
}