uva 11995 I Can Guess the Data Structure stack,queue,priority_queue

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<stack>
 5 #include<queue>
 6 using namespace std;
 7 int n;
 8 int v[1010],u[1010];
 9 
10 int ck_q()
11 {
12     //cout<<"!!"<<endl;
13     queue<int>s;
14     for(int i=0; i<n; i++)
15     {
16         if(v[i]==2)
17         {
18             if(s.empty())
19                 return 0;
20             int x=s.front();
21             s.pop();
22             if(x!=u[i])
23                 return 0;
24         }
25         else
26             s.push(u[i]);
27     }
28     return 1;
29 }
30 
31 int ck_s()
32 {
33     stack<int>s;
34     for(int i=0; i<n; i++)
35     {
36         if(v[i]==2)
37         {
38             if(s.empty())
39                 return 0;
40             int x=s.top();
41             s.pop();
42             if(x!=u[i])
43                 return 0;
44         }
45         else
46             s.push(u[i]);
47     }
48     return 1;
49 }
50 
51 int ck_d()
52 {
53     priority_queue<int>s;
54     for(int i=0; i<n; i++)
55     {
56         if(v[i]==2)
57         {
58             if(s.empty())
59                 return 0;
60             int x=s.top();
61             s.pop();
62             if(x!=u[i])
63                 return 0;
64         }
65         else
66             s.push(u[i]);
67     }
68     return 1;
69 }
70 int main()
71 {
72     while(~scanf("%d",&n))
73     {
74         for(int i=0; i<n; i++)
75         {
76             scanf("%d%d",&v[i],&u[i]);
77         }
78         int s=ck_s();
79         int q=ck_q();
80         int d=ck_d();
81         //cout<<s<<" "<<q<<" "<<d<<endl;
82         if(s&&!q&&!d)
83             printf("stack\n");
84         else if(!s&&q&&!d)
85             printf("queue\n");
86         else if(!s&&!q&&d)
87             printf("priority queue\n");
88         else if(!s&&!q&&!d)
89             printf("impossible\n");
90         else
91             printf("not sure\n");
92     }
93     return 0;
94 }