Leetcode/src/main/java/com/fishercoder/solutions/SpiralMatrixII.java at master · Dkra/Leetcode · GitHub

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package com.fishercoder.solutions;

/**
 * Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

 For example,
 Given n = 3,

 You should return the following matrix:
 [
 [ 1, 2, 3 ],
 [ 8, 9, 4 ],
 [ 7, 6, 5 ]
 ]
 */
public class SpiralMatrixII {

    public int[][] generateMatrix(int num) {
        int temp = num;
        int fourEdges[][] = new int[num][num];
        int  value = 1;
        int i = 0, j = 0;
        if(num%2 == 0)//when num is even
        {
            while(i < num/2 && j < num/2 && temp >= 0)
            {
				/* Assign the top row */
                while(j < temp)
                {
                    fourEdges[i][j] = value;
                    j++;
                    value++;

                }

				/* Assign the right column */
                while(i < temp - 1){
                    i++;
                    fourEdges[i][j - 1] = value;
                    value++;
                }
                j = j - 2;

				/* Assign the bottom row */
                while(j >= num - temp){
                    fourEdges[i][j] = value;
                    j--;
                    value++;
                }
                i--;
                j++;

				/* Assign the left column */
                while(i > num - temp){
                    fourEdges[i][j] = value;
                    i--;
                    value++;
                }
                //}
                i++;
                j++;
                temp--;
            }

        }
        else//when num is odd
        {
            while(i < num/2 && j < num/2 && temp >= 0)
            {
				/* Assign the top row */
                while(j < temp)
                {
                    fourEdges[i][j] = value;
                    j++;
                    value++;

                }

				/* Assign the right column */
                while(i < temp - 1){
                    i++;
                    fourEdges[i][j - 1] = value;
                    value++;
                }
                j = j - 2;

				/* Assign the bottom row */
                while(j >= num - temp){
                    fourEdges[i][j] = value;
                    j--;
                    value++;
                }
                i--;
                j++;

				/* Assign the left column */
                while(i > num - temp){
                    fourEdges[i][j] = value;
                    i--;
                    value++;
                }
                //}
                i++;
                j++;
                temp--;
            }
            fourEdges[num/2][num/2] = num*num;
        }

        for(int m = 0; m < num; m++){
            for(int n = 0; n < num; n++){
                System.out.print(fourEdges[m][n] + "\t");
                if((n+1) % num == 0)
                    System.out.println();
            }
        }
        return fourEdges;
    }

}