UVa11995 I Can Guess the Data Structure!

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

61 11 21 32 12 22 361 11 21 32 32 22 121 12 241 21 12 12 271 21 51 11 32 51 42 4

Output for the Sample Input

queuenot sureimpossiblestackpriority queue

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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!

这题其实也就是一个STL的应用题，对于n行的输入输出，判断是哪种容器符合，是queue/stack/priority queue还是not sure以及impossible。对于这题只要按照各个容器的用法使用，然后判断输入输出是否相符合即可。

#include <iostream>#include <queue>#include <stack>using namespace std;queue<int>q;stack<int>s;priority_queue<int>p;int main() {int Test;int order;int tmp;while (cin >> Test) {bool cnt_q = true;bool cnt_s = true;bool cnt_p = true;int cnt = 3;for (int i = 0; i < Test; i++) {cin >> order >> tmp;if (cnt_q) {if (order == 1)q.push(tmp);else if (!q.empty() && q.front() == tmp)q.pop();else {cnt--;cnt_q = false;}}if (cnt_s) {if (order == 1)s.push(tmp);else if (!s.empty() && s.top() == tmp)s.pop();else {cnt--;cnt_s = false;}}if (cnt_p) {if (order == 1)p.push(tmp);else if (!p.empty() && p.top() == tmp)p.pop();else {cnt--;cnt_p = false;}}}if (!cnt)cout << "impossible" << endl;else if (cnt > 1)cout << "not sure" << endl;else if (cnt_q)cout << "queue" << endl;else if (cnt_s)cout << "stack" << endl;elsecout << "priority queue" << endl;while (!q.empty())q.pop();while (!s.empty())s.pop();while (!p.empty())p.pop();}return 0;}