ZOJ 1259(Rails)

//使用两个栈和一个队列
#include<iostream>
#include<stack>
#include<queue>
using namespace std;
int main(void)
{
int n, temp;
while (cin>>n&&n)
{
while (cin >> temp&&temp)
{
stack<int>order, save; //save是一个暂存栈，象征着车站station
queue<int>check;  //check为待检查的（是否合法的、可能的出栈）序列
for (int i = n; i >= 1; i--)
{
order.push(i);
check.push(temp);
if (i != 1) cin >> temp;
}
//save和push底部都先放置了哨兵值0,以便以后易于判断
save.push(0);
check.push(0);
while (1)
{
if (check.front() == save.top())
{
check.pop();
save.pop();
}
else if (check.front() == order.top())
{
check.pop();
order.pop();
}
else
{
save.push(order.top());
order.pop();
}
if (order.empty() && save.top() && check.front() != save.top()) //关键
{
cout << "No" << endl;
break;
}
if (check.front() == 0) //check序列为“空（到底了）”
{
cout << "Yes" << endl;
break;
}
}
}
cout << endl;
}
return 0;
}