UVa 11955 I Can Guess the Data Structure!

UVa 19955 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 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). 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!

给你几组数据，1代表进，2代表出，输出是哪种数据结构（栈，队列，优先队列）。先将输入的数据记录下来，然后再一个个的试，看看是不是栈、队列或优先队列，然后按照题意输出就行了，不难，就是麻烦(｡•ˇ‸ˇ•｡)

[code]
 #include<iostream>
 #include <cstdio>
 #include <string.h>
 #include <queue>
 #include <stack>
using namespace std;
int main()
{
 #ifndef  ONLINE_JUDGE
    freopen("1.txt", "r", stdin);
 #endif
    int n, a;
    int i, j;
    int q[1000], p[1000];
    bool flag1, flag2, flag3;
    while(~scanf("%d", &n))
    {
        for (i = 0; i < n; i++)
        {
            cin >> q[i] >> p[i];
        }
        stack s;
        flag1 = true;
        for(i = 0; i < n; i++)
        {
            if (q[i] == 1)
            {
                s.push(p[i]);
            }
            else
            {
                if (s.empty())
                {
                    flag1 = false;
                    break;
                }
                else
                {
                    if (p[i] == s.top())
                    {
                        s.pop();
                    }
                    else
                    {
                        flag1 = false;
                        break;
                    }
                }
            }
        }
        flag2 = true;
        queue q1;
        for(i = 0; i < n; i++)
        {
            if (q[i] == 1)
            {
                q1.push(p[i]);
            }
            else
            {
                if (q1.empty())
                {
                    flag2 = false;
                    break;
                }
                else
                {
                    if (p[i] == q1.front())
                    {
                        q1.pop();
                    }
                    else
                    {
                        flag2 = false;
                        break;
                    }
                }
            }
        }
        flag3 = true;
        priority_queue pq;
        for (i = 0; i < n; i++)
        {
            if (q[i] == 1)
            {
                pq.push(p[i]);
            }
            else
            {
                if (pq.empty())
                {
                    flag3 = false;
                    break;
                }
                else
                {
                    if (p[i] == pq.top())
                    {
                        pq.pop();
                    }
                    else
                    {
                        flag3 = false;
                        break;
                    }
                }
            }
        }
        if (flag1 || flag2 || flag3)
        {
            if (flag1 + flag2 + flag3 > 1)
            {
                cout << "not sure" << endl;
            }
            else
            {
                if (flag1)
                {
                    cout << "stack" << endl;
                }
                else if (flag2)
                {
                    cout << "queue" << endl;
                }
                else if (flag3)
                {
                    cout << "priority queue" << endl;
                }
            }
        }
        else
        {
            cout << "impossible" << endl;
        }
    }
    return 0;
}