UVA - 11995 - I Can Guess the Data Structure! （基础数据结构练习！）

UVA - 11995

I Can Guess the Data Structure!

Time Limit: 1000MS

Memory Limit: Unknown

64bit IO Format: %lld & %llu

Submit Status

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 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!

好久没A题了，，今天刷会题，整理整理，，下个月恢复状态！！！！

大概题意：输入输出几组数据，，要你判断是哪一种数据结构（栈，队列，优先队列，或者全部是，或者两者及以上）

注意执行pop操作时要注意调用一下empty（），否则可能会异常退出。。。

思路：调用STL，，然后模拟其过程。。。

AC代码：

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <stack>
#include <queue>
using namespace std;

int main()
{
	int n;
	while(scanf("%d", &n) != EOF)
	{
		int st = 1, qu = 1, pr = 1;
		stack<int> s;
		queue<int> q;
		priority_queue<int> p;
		int a, b;
		while(n--)
		{
			scanf("%d %d", &a, &b);
			if(a == 1) 
			{
				s.push(b);
				q.push(b);
				p.push(b);
			}
			else 
			{
				if(!s.empty() && s.top() == b) s.pop();
				else st = 0;
				if(!q.empty() && q.front() == b) q.pop();
				else qu = 0;
				if(!p.empty() && p.top() == b) p.pop();
				else pr = 0;
			}
		}
		if(st + qu + pr >= 2) printf("not sure\n");
		else if(st == 1) printf("stack\n");
		else if(qu == 1) printf("queue\n");
		else if(pr == 1) printf("priority queue\n");
		else if(st == 0 && qu == 0 && pr == 0) printf("impossible\n");
	}
	return 0;
}