08-30 hdu_steps1 hdu2095

Solve some problems in hdu_step 1

1.2.2 hdu_2095 find your present (2)

Enter the number of n, where the number appears an odd number, to find the number

At first, we thought that both hash and map can be used. However, there is a simpler method for this question, that is, exclusive or operation.

0 ^ 6 = 0 6 ^ 6 = 0 a number is different or after two times it is equal to no operation

In addition, after the input plug-in is used, the time is reduced from 500 ms + to 60 ms, and the effect is obvious.

#include <cstdio>using namespace std;inline void scan(int &x){char c;   while(c=getchar(), c<'0'||c>'9');  x=c-'0';  while(c=getchar(), c>='0'&&c<='9') x=x*10+c-'0';}int main(){int n;while(scanf("%d",&n),n){int tmp=0,x;for(int i=0;i<n;i++){scan(x);tmp^=x;}printf("%d\n",tmp);}}

Other questions in step 1 are very watery ..