LeetCode | Spiral Matrix

题目

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

For example,
Given the following matrix:

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

You should return [1,2,3,6,9,8,7,4,5].

这题没用到什么特别的技巧，就是一层一层来，需要注意一些边界条件。

代码

import java.util.ArrayList;

public class SpiralMatrix {
	public ArrayList
  
    spiralOrder(int[][] matrix) {
		ArrayList
   
     list = new ArrayList
    
     (); if (matrix == null || matrix.length == 0) { return list; } int minRow = 0; int minColumn = 0; int maxRow = matrix.length - 1; int maxColumn = matrix[0].length - 1; while (minRow <= maxRow && minColumn <= maxColumn) { for (int i = minColumn; i <= maxColumn; ++i) { list.add(matrix[minRow][i]); } for (int i = minRow + 1; i <= maxRow; ++i) { list.add(matrix[i][maxColumn]); } if (minRow != maxRow) { for (int i = maxColumn - 1; i >= minColumn; --i) { list.add(matrix[maxRow][i]); } } if (minColumn != maxColumn) { for (int i = maxRow - 1; i > minRow; --i) { list.add(matrix[i][minColumn]); } } ++minRow; ++minColumn; --maxRow; --maxColumn; } return list; } }