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;}