Kattis -I Can Guess the Data Structure!

I Can Guess the Data Structure!

There is a bag-like data structure, supporting two operations:

$1 x$

$2$

Given a sequence of operations with return values, you’re going to guess the data structure. It is a stack (Last-In, First-Out), a queue (First-In, First-Out), a priority-queue (Always take out larger elements first) or something else that you can hardly imagine!

Input

There are several test cases. Each test case begins with a line containing a single integer $n$

Output

For each test case, output one of the following:

stack
It’s definitely a stack.

queue
It’s definitely a queue.

priority queue
It’s definitely a priority queue.

impossible
It can’t be a stack, a queue or a priority queue.

not sure
It can be more than one of the three data structures mentioned above.

Sample Input 1	Sample Output 1
6 1 1 1 2 1 3 2 1 2 2 2 3 6 1 1 1 2 1 3 2 3 2 2 2 1 2 1 1 2 2 4 1 2 1 1 2 1 2 2 7 1 2 1 5 1 1 1 3 2 5 1 4 2 4 1 2 1	queue not sure impossible stack priority queue impossible

题意

模拟栈stack，队列queue，和优先队列priority queue的进出，判断属于哪一个

思路

用stl模拟

代码

#include<bits/stdc++.h>
using namespace std;
int main() {
    int n, a, x;
    while(cin >> n) {
        stack<int> s;
        queue<int> q;
        priority_queue<int> pq;
        bool iss = 1, isq = 1, ispq = 1;
        while(n--) {
            cin >> a >> x;
            if(a == 1) {
                s.push(x);
                q.push(x);
                pq.push(x);
            } else {
                if(s.empty() || s.top() != x) iss = 0;
                if(q.empty() || q.front() != x) isq = 0;
                if(pq.empty() || pq.top() != x) ispq = 0;
                if(!s.empty()) s.pop();
                if(!q.empty()) q.pop();
                if(!pq.empty()) pq.pop();
            }
        }
        if(iss + isq + ispq > 1)
            puts("not sure");
        else if(iss)
            puts("stack");
        else if(isq)
            puts("queue");
        else if(ispq)
            puts("priority queue");
        else
            puts("impossible");
    }
}