UVA-11995：I Can Guess the Data Structure!

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来源：UVA

标签：数据结构

参考资料：

相似题目：

题目

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

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!

输入

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 x without error. The value of x is always a positive integer not larger than 100. The input is terminated by end-of-file (EOF).

输出

For each test case, output one of the following:

输入样例

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

输出样例

queue
not sure
impossible
stack
priority queue

题目大意

解题思路

参考代码

#include<stdio.h>
#include<stack>
#include<queue>
#define MAXN 1000
using namespace std;

int main(){
    int n;
    while(scanf("%d",&n)!=EOF){
        int type, num;
        int flag=7, sf=1, qf=2, pqf=4;
        stack<int> s;
        queue<int> q;
        priority_queue<int> pq;
        for(int i=0;i<n;i++){
            scanf("%d%d",&type,&num);
            if(type==1){
                s.push(num);
                q.push(num);
                pq.push(num);
            }
            else{
                if(sf){
                    if(s.empty() || !s.empty()  && s.top()!=num){
                        flag-=sf;
                        sf=0;       
                    }else s.pop();
                }
                if(qf){
                    if(q.empty() || !q.empty()  && q.front()!=num){
                        flag-=qf;
                        qf=0;       
                    }else q.pop();
                }
                if(pqf){
                    if(pq.empty() || !pq.empty()  && pq.top()!=num){
                        flag-=pqf;
                        pqf=0;      
                    }else pq.pop();
                }
            }
        }
        if(flag==1){
            printf("stack\n");
        }else if(flag==2){
            printf("queue\n");
        }else if(flag==4){
            printf("priority queue\n");
        }else if(flag>0){
            printf("not sure\n");
        }else 
            printf("impossible\n");
    }
    return 0;
}