UVa 514 铁轨

题意：

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    int num[];
    int kase = ;
    while(scanf("%d", &n) != EOF && n != )
    {
        while(scanf("%d", &num[]) && num[] != ){
            stack<int> s1;
            num[] = num[];
            for(int i = ; i <= n; i++){
                scanf("%d", num+i);
            }
            int ok = ;
            int A = , B = ;
            while(B <= n){
                if(A == num[B]){A++; B++;}
                else if(!s1.empty() && s1.top() == num[B]){s1.pop(); B++;}
                else if(A <= n) s1.push(A++);
                else {ok =; break;};
            }
            if(ok) printf("Yes\n");
            else printf("No\n");
        }
        printf("\n");
    }
}