Solved

2d array rotation

Posted on 2011-03-23
3
3,480 Views
Last Modified: 2012-05-11
how to rotate a 2d array (matrix) 90 degrees anticlockwise so:

X =
    1    2    3
    4    5    6
    7    8    9

becomes

Y =
    3    6    9
    2    5    8
    1    4    7
0
Comment
Question by:chudyksg
3 Comments
 
LVL 40

Expert Comment

by:gurvinder372
Comment Utility
create another empty array of 3x3 dimension, and follow these steps

pick value at 1,1 and put it at 3,1
pick value at 1,2 and put it at 2,1
pick value at 1,3 and put it at 1,1
pick value at 2,1 and put it at 3,2
pick value at 2,3 and put it at 1,2
pick value at 3,1 and put it at 3,3
pick value at 3,2 and put it at 2,3
pick value at 3,3 and put it at 1,3
0
 
LVL 27

Accepted Solution

by:
rrz earned 500 total points
Comment Utility
from
http://stackoverflow.com/questions/42519/how-do-you-rotate-a-two-dimensional-array
public int[][] rotateMatrixLeft(int[][] matrix)
{
    /* W and H are already swapped */
    int w = matrix.length;
    int h = matrix[0].length;   
    int[][] ret = new int[h][w];
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            ret[i][j] = matrix[j][h - i - 1];
        }
    }
    return ret;
}

Open in new window

0
 

Expert Comment

by:sinsach
Comment Utility
This will rotate any matrix 90 degrees anti-clock.

/**
* To rotate the array 90 degrees anti-clock wise. This will rotate square
* and non square matrix.
* 
* @param sourceArray
* @return
*/
public int[][] antiClock90Rotation(int[][] sourceArray) {
	int[][] rotatedArray = new int[sourceArray[0].length][sourceArray.length];
	int positionFactor = rotatedArray.length - 1;
	for (int i = 0; i < rotatedArray.length; i++) {
		for (int j = 0; j < rotatedArray[i].length; j++) {
			int a = i - positionFactor;
			a = (a < 0) ? -a : a;
			rotatedArray[i][j] = sourceArray[j][a];
		}
	}
	return rotatedArray;
}

Open in new window

0

Featured Post

What Security Threats Are You Missing?

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

Join & Write a Comment

Suggested Solutions

By the end of 1980s, object oriented programming using languages like C++, Simula69 and ObjectPascal gained momentum. It looked like programmers finally found the perfect language. C++ successfully combined the object oriented principles of Simula w…
Java functions are among the best things for programmers to work with as Java sites can be very easy to read and prepare. Java especially simplifies many processes in the coding industry as it helps integrate many forms of technology and different d…
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
Viewers learn how to read error messages and identify possible mistakes that could cause hours of frustration. Coding is as much about debugging your code as it is about writing it. Define Error Message: Line Numbers: Type of Error: Break Down…

728 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

9 Experts available now in Live!

Get 1:1 Help Now