Leetcode 54 Spiral Matrix Java Solution

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

Example 1:

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

Example 2:

Input:
[
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9,10,11,12]
]
Output: [1,2,3,4,8,12,11,10,9,5,6,7]

Solution 1:

class Solution {
    
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> spiral = new ArrayList<Integer>();
        if(matrix.length == 0) return spiral;
        int m = matrix.length;
        int n = matrix[0].length;
        int i =0;
        int j = 0;
        int k;
        
        
        while(i<m && j<n){
            for( k=j;k<n;k++){
                spiral.add(matrix[i][k]);
            }
            i++;
            for(k=i;k<m;k++){
                spiral.add(matrix[k][n-1]);
            }
            n--;
            
            if(i<m){
                for(k = n-1;k>=j;--k){
                    spiral.add(matrix[m-1][k]);
                }
                m--;
            }
            
            if(j<n){
                for(k=m-1;k>=i;--k){
                    spiral.add(matrix[k][j]);
                }
                j++;
            }
        }
        
        return spiral;
    }
}