Main.java

import java.awt.Point;

public class Main {
	public static int[][] create2dArray(int size) {
		int[][] array = new int[size][size];
		
		for(int row = 0; row < size; ++row) {
			for(int col = 0; col < size; ++col) {
				array[row][col] = (col + 1) + size * row;
			}
		}
		
		return array;
	}
	
	public static void print2dArray(int[][] array) {
		for(int[] row : array) {
			for(int element : row) {
				System.out.print(element + "\t");
			}
			System.out.println();
		}
	}

	public static int[][] spiralizeArray(int[][] array) {
		int arraySize = array[0].length;
		int[][] spiralArray = new int[arraySize][arraySize];
		Point position = new Point((arraySize - 1) / 2, (arraySize - 1) / 2);
		Direction directionToMove = Direction.RIGHT;
		int distanceToMove = 1;
		int totalMovementInDirection = 1;
		
		for(int i = 0; i < arraySize * arraySize; ++i) {
			// Uncomment this line to see the position we're at in the spiral
			//System.out.println("Spiral: (" + position.x + ", " + position.y + ")");
			
			// Uncomment this line to see the position we're at in the original
			//System.out.println("Original: (" + (i / arraySize) + ", " + (i % arraySize) + ")");
			
			// Copy the ith value to the position placement
			spiralArray[position.x][position.y] = array[i / arraySize][i % arraySize];
			
			// We've exhausted a move in that direction
			--distanceToMove;
			
			// If we're changing from moving up or down, then the distance we move
			// will increase.
			if(distanceToMove == 0 && (directionToMove == Direction.UP ||
					directionToMove == Direction.DOWN)) {
				++totalMovementInDirection;
			}

			// Figure out which way to move in. While we're at it, figure out the
			// new direction if we've reached the end of where to move
			if(directionToMove == Direction.UP) {
				position.translate(-1, 0);
				if(distanceToMove == 0) directionToMove = Direction.RIGHT;
			}
			else if(directionToMove == Direction.DOWN) {
				position.translate(1, 0);
				if(distanceToMove == 0) directionToMove = Direction.LEFT;
			}
			else if(directionToMove == Direction.LEFT) {
				position.translate(0, -1);
				if(distanceToMove == 0) directionToMove = Direction.UP;
			}
			else {
				position.translate(0, 1);
				if(distanceToMove == 0) directionToMove = Direction.DOWN;
			}
			
			// And if we reached 0 distance to move, that gets reset
			if(distanceToMove == 0) {
				distanceToMove = totalMovementInDirection;
			}
		}
		
		return spiralArray;
	}
	
	private enum Direction { UP, DOWN, LEFT, RIGHT }
	
	public static void main(String[] args) {
		int[][] array = create2dArray(4);
		int[][] spiral = spiralizeArray(array);
		
		System.out.println("ORIGINAL:");
		print2dArray(array);

		System.out.println("SPIRAL:");
		print2dArray(spiral);
	}
}