UVA - 514 Rails

#include <iostream>
#include <stack>
using namespace std;
const int N = 1000 + 10;

int n, target
;
//target数组用来记录，题目所要求的，进入B方向的n个火车的依次序号
int main()
{
while (cin >> n && n)
{
stack<int> s;
while (cin >> target[1] && target[1])
{
int A = 1, B = 1; //B表示，来自A方向的车厢判断到哪一节，A表示，进入B方向的车厢，判断到哪个下标了
for (int i = 2; i <= n; i++)
cin >> target[i];

int ok = 1;
while (B <= n)
{
if (A == target[B])
{
A++; B++;
}
else if (!s.empty() && s.top() == target[B])
{
s.pop();
B++;
}
else if (A <= n)
{
s.push(A++);
}
else
{
ok = 0;
break;
}
}
cout << (ok ? "Yes" : "No") << endl;
}
cout << endl;
}
return 0;
}