The 9th Zhejiang University Programming Contest I

题目在这里：http://acm.zju.edu.cn/onlinejudge/showContestProblem.do?problemId=3214

#include <iostream>
using namespace std;
unsigned int gray2dec(unsigned int x) {
 unsigned int y = x; while(x>>=1) y ^= x; return y;
}
int main() {
 int N,n;
 for(cin>>N;N;--N){
     cin>>n; cout<<gray2dec((1<<n)-1)<<endl;
 }
 return 0;
}