54. Spiral Matrix

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

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]

class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List result = new ArrayList();
        if(matrix.length < 1){
            return result;
        }
        
        int rows = matrix.length;
        int cols = matrix[0].length;
        
        boolean[][] visit = new boolean[rows][cols];
        int[][] dirs = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
        int d = 0;
        int m = 0;
        int n = 0;
        
        for(int i=0; i<matrix.length * matrix[0].length; i++){
            result.add(matrix[m][n]);
            visit[m][n] = true;
            
            if(dirs[d][0]+m<0 || rows-1<dirs[d][0] + m ||
               dirs[d][1]+n<0 || cols-1<dirs[d][1]+n ||
               visit[dirs[d][0]+m][dirs[d][1]+n] == true){
                d = (d+1)%4;
            }
            m = dirs[d][0] + m;
            n = dirs[d][1] + n;
        }
        
        return result;
    }
}

[문제] https://leetcode.com/problems/spiral-matrix/