By Rujia Liu China
There is a bag-like data structure, supporting two operations:
Throw an element x into the bag.
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!
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.
For each test case, output one of the following:
It's definitely a stack.
It's definitely a queue.
It's definitely a priority queue.
It can't be a stack, a queue or a priority queue.
It can be more than one of the three data structures mentioned above.
|Sample Input||Sample Output|