1041 Be Unique

description

Being unique is so important to people on Mars that even（甚至） their lottery（彩票） is designed in a unique way. The rule of winning is simple（简单的）: 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

solution

找首个只出现了一次的数字，若无则为None。
和前面几题稍有不同，不是直接找出现次数。加了需要首次出现的条件。

#include 
int main(){
	int hash[10001] = {0}, n, a[100005];
	scanf("%d", &n);
	for(int i = 1; i <= n; i++){
		scanf("%d", a + i);
		hash[a[i]]++;
	}
	for(int i = 1; i <= n; i++){
		if(hash[a[i]] == 1){
			printf("%d", a[i]);
			return 0;
		}
	}
	printf("None");
	return 0;
}