寻找只出现一次的数
1. 原文
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,$10^4$]. 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 (≤$10^5$) 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:
1 | 7 5 31 5 88 67 88 17 |
Sample output 1:
1 | 31 |
Sample Input 2:
1 | 5 888 666 666 888 888 |
Sample output 2:
1 | None |
2. 解析
输出仅出现一次的数
3. AC代码
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