剑指 Offer - 19：顺时针打印矩阵

题目描述

输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字，例如，如果输入如下4 X 4矩阵：
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
则依次打印出数字：1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10

题目链接：https://www.nowcoder.com/practice/9b4c81a02cd34f76be2659fa0d54342a

// 模拟
public class Solution {
    public ArrayList<Integer> printMatrix(int [][] matrix) {
        int left = 0;
        int right = matrix[0].length - 1;
        int top = 0;
        int bottom = matrix.length - 1;
        ArrayList<Integer> result = new ArrayList<>();
        if (right < 0 || bottom < 0) return result;
        while (left <= right && top <= bottom) {
            for (int i = left; i <= right; i++) {
                result.add(matrix[top][i]);
            }
            for (int i = top+1; i <= bottom; i++) {
                result.add(matrix[i][right]);
            }
            if (top != bottom) {
                for (int i = right-1; i >= left; i--) {
                    result.add(matrix[bottom][i]);
                }
            }
            if (left != right) {
                for (int i = bottom-1; i >= top+1; i--) {
                    result.add(matrix[i][left]);
                }
            }
            left++;
            right--;
            top++;
            bottom--;
        }
        return result;
    }
}