順時針列印矩陣 java

題目描述
輸入一個矩陣，按照從外向裡以順時針的順序依次打印出每一個數字，例如，如果輸入如下4 X 4矩陣： 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 則依次打印出數字1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.

程式碼1：

import java.util.ArrayList;

public class Solution {
    public ArrayList<Integer> printMatrix(int [][] matrix) {
        ArrayList<Integer> al = new ArrayList<>();
        int row = matrix.length, col = matrix[0].length;
        int left = 0, right = col - 1;
        int top = 0, bottom = row - 1;
        if(matrix == null){
            return null;
        }
        while(left <= right && top <= bottom){
            //從左到右列印
            for(int i = left; i <= right; i++){
                al.add(matrix[top][i]);
            }
            //從上到下列印
            if(top != bottom){
                for(int i = top + 1; i <= bottom; i++){
                    al.add(matrix[i][right]);
                }
            }
            //從右到左列印
            if(top != bottom){
                for(int i = right - 1; i >= left; i--){
                    al.add(matrix[bottom][i]);
                }
            }
            //從下到上列印
            if(left != right){
                for(int i = bottom - 1; i > top; i--){
                    al.add(matrix[i][left]);
                }
            }
            left++; right--;
            top++; bottom--;
        }
        return al;
    }
}