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=1000+10;  
使用栈  
int n,target[maxn];  
int main()  
{  
    while(scanf("%d",&n)==1)  
     {  
      stack<int> s;//生成一个元素为int的栈吧；  
      int A=1,B=1;  
      for(int i=1;i<=n;i++)  
         scanf("%d",&target[i]);//读入出栈顺序；  
      int ok =1;  
      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=0;break;}  
       }  
    printf("%s\n",ok?"Yes":"No");  
    }  
 return 0;  
}