1041. Be Unique (20) Hash散列

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:

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:

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：

给定一个数N 和N个数，要求求出这N个数中第一个独一无二的数（即与其他N-1个数是不相同的）

分析：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

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#include <set>
using namespace std;
const int maxn = 1e5+10;
int a[maxn],m[maxn];
int main()
{
    int n;
    cin >> 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;
}