poj 1363 Rails

#include<cstdio>#include<stack>#include<cstring>#include<cstdlib>using namespace std;int main(){    int i,j,k,T;    int num,flag;    while(scanf("%d",&T),T)    {        flag=0;//必须再次初始化为0         while(1)        { stack <int> s; int temp=1; s.push(temp); for(i=1;i<=T;i++) {        scanf("%d",&num);     if(0==num)     {         flag=1;         break;     }     if(s.empty())     {         temp++;         s.push(temp);     }     int top=s.top();     while(top!=num)     {         if(temp==T) break;         temp++;         s.push(temp);         top=s.top();     }     if(top==num)         s.pop(); } if(flag)     break; if(s.empty())     puts("Yes"); else     puts("No");        }        printf("n");    }    return 0;}