PAT-A 1041. Be Unique

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

程序代码：

#include<stdio.h>
#define MAX 100000
int a[MAX];
int b[10001]={0};
int main()
{
    int n,i;
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
        b[a[i]]++;  
    }
    for(i=0;i<n;i++)
    {
        if(b[a[i]]==1)
        {
            printf("%d",a[i]);
            return 0;
        }
    }
    printf("None");
    return 0;   
}