出栈顺序判断

#include<iostream>
#include<fstream>
#include<stack>
#include<sstream>
using namespace std;

int main()
{
ifstream in("stack.txt");
for (int n, line = 0; in >> n&&n&&in.ignore();)
{
cout << (line++ ? "\n" : "");
for (string s; getline(in, s) && s != "0";)
{
istringstream sin(s);
stack<int> st;
for (int last = 0, coach; sin >> coach; st.pop())
{

for (int p = last + 1; p <= coach; p++)
st.push(p);
if (last < coach)
last = coach;
if (st.top ()!= coach)
break;

}
cout << (!sin ? "YES\n" : "NO\n");
}
}
}