Win a copy of Functional Design and Architecture this week in the Functional programming forum!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Ron McLeod
  • Rob Spoor
  • Tim Cooke
  • Junilu Lacar
Sheriffs:
  • Henry Wong
  • Liutauras Vilda
  • Jeanne Boyarsky
Saloon Keepers:
  • Jesse Silverman
  • Tim Holloway
  • Stephan van Hulst
  • Tim Moores
  • Carey Brown
Bartenders:
  • Al Hobbs
  • Mikalai Zaikin
  • Piet Souris

Rotating a matrix

 
Bartender
Posts: 4619
182
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
I was doing some exercise where I frequently needed to rotate or flip a 2D rectangular array (matrix).

Now, one way to do such thing is to have two nested loops, and swap the corresponding elements. But that means what I call 'a lot of index juggling'.

Suppose we have the methods 'int[] getColumn(int[][] array, int column)' and 'int[] reverse(int[] array)'.

When we rotate a matrix right, then we see that column 0 becomes row 0, albeit reversed. So our method can become:

Can you find similar methods for rotating left and flipping horizontally or vertically?
 
You showed up just in time for the waffles! And this tiny ad:
Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop
https://coderanch.com/wiki/718759/books/Building-World-Backyard-Paul-Wheaton
reply
    Bookmark Topic Watch Topic
  • New Topic