UVA19955 I Can Guess the Data Structure! STL

根据题目给出的数据输入和输出，判断是栈，队列和优先队列中那种数据结构的题目

I Can Guess the Data Structure!

Time Limit: 1000MS

Memory Limit: Unknown

64bit IO Format: %lld & %llu

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Description

Problem I

I Can Guess the Data Structure!

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

1 x

Throw an element x into the bag.

2

Take out an element from the bag.

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 (1<=n<=1000). Each of the next n lines is either a type-1 command, or an integer 2 followed by an integer x. That means after executing a type-2 command, we get an element xwithout error. The value of x is always a positive integer not larger than 100. The input is terminated by end-of-file (EOF). The size of input file does not exceed 1MB.

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

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

Output for the Sample Input

queue
not sure
impossible
stack
priority queue

---

Rujia Liu's Present 3: A Data Structure Contest Celebrating the 100th Anniversary of Tsinghua University
Special Thanks: Yiming Li
Note: Please make sure to test your program with the gift I/O files before submitting!

#include<iostream>
#include<cstdio>
#include<cstring>
#include<stack>
#include<queue>

using namespace std;

int n;

void solve()
{
    bool iss,isq,ispq;
    stack<int> s;
    queue<int> q;
    priority_queue<int> pq;
    iss=1,isq=1,ispq=1;
    int x,y,z;
    for(int i=0;i<n;i++)
    {
        scanf("%d%d",&x,&y);
        if(x==1)
        {
            if(iss) s.push(y);
            if(isq) q.push(y);
            if(ispq)pq.push(y);
        }
        else
        {
            if(iss)
            {
                if(s.empty())
                    iss=0;
                else
                {
                    z=s.top();
                    s.pop();
                    if(z!=y) iss=0;
                }
            }
            if(isq)
            {
                if(q.empty())
                    isq=0;
                else
                {
                    z=q.front();
                    q.pop();
                    if(z!=y) isq=0;
                }
            }
            if(ispq)
            {
                if(pq.empty())
                    ispq=0;
                else
                {
                    z=pq.top();
                    pq.pop();
                    if(z!=y) ispq=0;
                }
            }
        }
    }
    if(iss && !isq && !ispq)
        printf("stack\n");
    else if(!iss && isq && !ispq)
        printf("queue\n");
    else if(!iss && !isq && ispq)
        printf("priority queue\n");
    else if(!iss && !isq && !ispq)
        printf("impossible\n");
    else printf("not sure\n");
}

int main()
{
    while(~scanf("%d",&n))
        solve();
    return 0;
}