the railway problem(the example of stack)

this problem is a very classic problem which can use stack to solve. the problem can be searched through many source site.

#include<cstdio>
#include<stack>//表明要调用关于栈的文件吧；
using namespace std;
const int maxn=+;
使用栈
int n,target[maxn];
int main()
{
    while(scanf("%d",&n)==)
     {
      stack<int> s;//生成一个元素为int的栈吧；
      int A=,B=;
      for(int i=;i<=n;i++)
         scanf("%d",&target[i]);//读入出栈顺序；
      int ok =;
      while(B<=n)
       {
        if(A==target[B]){A++;B++;}//进等于出就直接出；
        else if(!s.empty()&&s.top()==target[B])
                 {s.pop();B++;}//如果S不为空栈并且s的栈顶元素正好为需要的B元素就直接把顶端元素放出去；
        else if(A<=n)s.push(A++);//还有合法的未进栈元素就让其进栈；
        else {ok=;break;}
       }
    printf("%s\n",ok?"Yes":"No");
    }
 return ;
}