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.
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.
For each test case, print the winning number in a line. If there is no winner, print None instead.
7 5 31 5 88 67 88 17
31
5 888 666 666 888 888
None
题意：
给出n个数字，要求输出第一个只出现一次的数字，如果不存在，输出None.
题解：
用类似打表的方法，统计每个数出现的次数。按输出顺序遍历，当有次数为1的数时，输出，没有就输出None。
AC代码：
#include<iostream> #include<algorithm> #include<vector> #include<queue> #include<map> #include<string> #include<cstring> using namespace std; int a[10005]; int shu[100005]; int main() { int n; cin>>n; memset(a,0,sizeof(a)); for(int i=1;i<=n;i++){ cin>>shu[i]; a[shu[i]]++; } int f=0; for(int i=1;i<=n;i++){ if(a[shu[i]]==1){ cout<<shu[i]; f=1; break; } } if(!f) cout<<"None"; return 0; }
PAT 甲级 1041 Be Unique (20 分)（简单,一遍过）
原文：https://www.cnblogs.com/caiyishuai/p/11438337.html