Algorithms and Data Structures

  • Profound Academy

    • Status
      • 1
        Implementation
      • 2
        Bitwise operations
      • 3
        Prefix Sums
      • 4
        Sliding window / Two pointers
      • 5
        Modular Arithmetic
      • 6
        Number Theory
      • 7
        Binary Search
      • 8
        Basic Sorting
      • 9
        Greedy Algorithms
      • 10
        Basic Dynamic Programming
      • 11
        Recursion
      • 12
        Linked LIst
      • 13
        Queue & Stack
      • 14
        Binary tree + BST
      • 15
        Divide & Conquer + Advanced Sorting
      • 16
        Heap
      • 17
        Hashing
      • 18
        Graph Representation
      • 19
        BFS

    • Designing an operating system

    Linus Torvalds, the creator of the Linux operating system, has decided to trust you with the maintenance of the codebase for the operating system. Yet, as you like to experiment, you have decided to rewrite some of the most popular commands and deploy them to production.
    notion image
    This week you’re rewriting the pwd (print working directory) and the cd (change directory) commands. You would like to have those commands working based on the user input:
    1. If the user inputs pwd - the program should print the current working directory
    1. If the user inputs cd folder - the program should move to that folder:
        • If the folder is .. - it means that the program should move to the parent directory. So, if we’re at directory /usr/local/bin/, the program should move to /usr/local/.
        • If the folder is . - it means that the program should stay in the current directory.
        • If the folder starts with /, it means that the program should change the absolute path of the directory - not the relative. So, if we’re at directory /usr/local/bin/, and the input was cd /dev, the program should move to /dev/.
        • If the folder is a name (Latin letters or numbers) - the program should move to that directory relative to the current one. So, if we’re at directory /usr/local/bin/, and the input was cd ../lib, the program should move to /usr/local/lib/.
    The program is initiated at the location / (which is the root of the file system).

    Input

    The first line of the input contains a single integer n (1 ≤ n ≤ 100) the number of commands.
    The next n lines contain the commands. It’s guaranteed that the length of each command does not exceed 200 characters.

    Output

    The programs should print the results for all the pwd commands each on a separate line.

    Examples

    Input
    Output
    5 pwd cd usr/local/bin cd .. pwd cd /dev
    / /usr/local/
    7 pwd cd /home/anna pwd cd .. pwd cd anna/../bob pwd
    / /home/anna/ /home/ /home/bob/
    4 cd /usr/local pwd cd ../usr/local pwd
    /usr/local/ /usr/usr/local/
     

    Constraints

    Time limit: 1 seconds

    Memory limit: 512 MB

    Output limit: 1 MB

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