LeetCode 54. Spiral Matrix

Question

Given an m x n matrix, return all elements of the matrix in spiral order.

https://leetcode.com/problems/spiral-matrix/

• Solution1

class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> res = new LinkedList<Integer>();
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) return res;
        int left = 0, right = matrix[0].length - 1;
        int top = 0, bottom = matrix.length - 1;
        while (left < right && top < bottom) {
            for (int i = left; i < right; i++) res.add(matrix[top][i]);
            for (int i = top; i < bottom; i++) res.add(matrix[i][right]);
            for (int i = right; i > left; i--) res.add(matrix[bottom][i]);
            for (int i = bottom; i > top; i--) res.add(matrix[i][left]);
            left++;
            right--;
            top++;
            bottom--;
        }
        if (left == right) {
            for (int i = top; i <= bottom; i++) res.add(matrix[i][left]);
        } else if (top == bottom) {
            for (int i = left; i <= right; i++) res.add(matrix[top][i]);
        }
        return res;
    }
}

Complexity:

Time complexity: O(mn)

Space complexity: O(mn)