UVa 514（栈）铁轨

#include<iostream>
using namespace std;
int s[100000],top;
int main()
{
    int n,t;
    while(scanf("%d",&n)&&n)
    {
        while(1)
        {
            int f=0;
            int k=1,top=1;
            scanf("%d",&t);
            if(t==0) break;
            while((top==1||s[top-1]!=t)&&k<=n) s[top++]=k++;
            if(top>1&&s[top-1]==t) --top;
            else f=1;
            for(int i=1; i<n; ++i)
            {
                scanf("%d",&t);
                if(f) continue;
                 while((top==1||s[top-1]!=t)&&k<=n) s[top++]=k++;
                if(top>1&&s[top-1]==t) --top;
                else f=1;
            }
            puts(!f?"Yes":"No");
        }
        puts("");
    }
    return 0;
}