poj 1392 Ouroboros Snake

#include<cstdio>#include<cstring>#include<iostream>using namespace std;const int maxn=1<<16;int n,m,k,top,len,cnt[maxn],ans[maxn];void DFS(int v){    while(cnt[v]<2)    {int w=(v<<1)+cnt[v];cnt[v]++;DFS(w&m);ans[len++]=w;    }}int main(){    while(scanf("%d%d",&n,&k)&&(n+k))    {top=len=0;memset(cnt,0,sizeof(cnt));m=(1<<(n-1))-1;DFS(0);while(k--)    len--;printf("%dn",ans[--len]);    }    return 0;}