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). Output For each test case, output one of the following: stack queue priority queue impossible Sample Input 6 11 12 13 21 22 23 6 11 12 13 23 22 21 2 11 22 4 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. not sure It can be more than one of the three data structures mentioned above.
11995 – I Can Guess the Data Structure! 2/2 12 11 21 22 7 12 15 11 13 25 14 24 Sample Output queue not sure impossible stack priority queue