[Codewar] The Clockwise Spiral

https://www.codewars.com/kata/the-clockwise-spiral/java

Codewars: Train your coding skills

 

Do you know how to make a spiral? Let's test it!

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Classic definition: A spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.

 

 

Your objective is to complete a function createSpiral(N) that receives an integer N and returns an NxN two-dimensional array with numbers 1 through NxN represented as a clockwise spiral.

Return an empty array if N < 1 or N is not int / number

 

Examples:

N = 3 Output: [[1,2,3],[8,9,4],[7,6,5]]

1    2    3    
8    9    4    
7    6    5    

N = 4 Output: [[1,2,3,4],[12,13,14,5],[11,16,15,6],[10,9,8,7]]

1   2   3   4
12  13  14  5
11  16  15  6
10  9   8   7

N = 5 Output: [[1,2,3,4,5],[16,17,18,19,6],[15,24,25,20,7],[14,23,22,21,8],[13,12,11,10,9]]

1   2   3   4   5    
16  17  18  19  6    
15  24  25  20  7    
14  23  22  21  8    
13  12  11  10  9

 

 

 

Solution

public class TheClockwiseSpiral {

    public static int[][] createSpiral(int N) {
        int[][] list = new int[N][N];
		int cnt = 1;
    		int rot = 1;
        	int a=0 ,b=-1;

		
    		while(N>0) {
    			for(int i=0; i<N; i++){
    				b+=rot;
    				list[a][b] = cnt;
    				cnt++;
    			}
    			N--;
  
    			for(int i=0; i<N; i++){
    				a+=rot;
    				list[a][b] = cnt;
    				cnt++;
    			}
    			rot*=-1;
    		}
        
        return list;
    }
}