HDOJ find your present (2) 2095

find your present (2)

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 17902    Accepted Submission(s): 6859

Problem Description

In the new year party, everybody will get a "special present".Now it's your turn to get your special present, a lot of presents now putting on the desk, and only one of them will be yours.Each present has a card number on it, and your present's card number will be the one that different from all the others, and you can assume that only one number appear odd times.For example, there are 5 present, and their card numbers are 1, 2, 3, 2, 1.so your present will be the one with the card number of 3, because 3 is the number that different from all the others.

 

 

Input

The input file will consist of several cases.
Each case will be presented by an integer n (1<=n<1000000, and n is odd) at first. Following that, n positive integers will be given in a line, all integers will smaller than 2^31. These numbers indicate the card numbers of the presents.n = 0 ends the input.

 

 

Output

For each case, output an integer in a line, which is the card number of your present.

 

 

Sample Input

51 1 3 2 231 2 10

 

 

Sample Output

32
Hint
Hint
 use scanf to avoid Time Limit Exceeded

 

 

Author

8600

 

 

Source

HDU 2007-Spring Programming Contest - Warm Up （1）

 

 

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异或的性质

1. 交换律：a ^ b = b ^ a
2. 结合律：a ^ b ^ c = a ^ (b ^ c) = (a ^ b) ^ c
3. d = a ^ b ^ c 可以推出 a = d ^ b ^ c
4. 自反性：a ^ b ^ a = b

运用自反性。

 

#include<stdio.h>#include<algorithm>using namespace std;int main(){int t;while(scanf("%d",&t),t){int res=0;int a;while(t--){scanf("%d",&a);res=res^a;//}printf("%d\n",res);}return 0;}