剑指offer | 面试题22：顺时针打印矩阵

输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
输出：[1,2,3,6,9,8,7,4,5]

输入：matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
输出：[1,2,3,4,8,12,11,10,9,5,6,7]

package com.nateshao.sword_offer.topic_22_spiralOrder;

/**
 * @date Created by 邵桐杰 on 2021/11/25 9:59
 * @微信公众号 程序员千羽
 * @个人网站 www.nateshao.cn
 * @博客 https://nateshao.gitee.io
 * @GitHub https://github.com/nateshao
 * @Gitee https://gitee.com/nateshao
 * Description: 剑指 Offer 22. 顺时针打印矩阵
 * https://leetcode-cn.com/problems/shun-shi-zhen-da-yin-ju-zhen-lcof
 */
public class Solution {

    public static void main(String[] args) {
        int[][] matrix = {{1, 2, 3},
                {4, 5, 6},
                {7, 8, 9}};
        printMatrix(matrix);
        spiralOrder(matrix);
        System.out.println("=========");
        printMatrix(matrix);
    }

    public static void printMatrix(int[][] matrix) {
        for (int i = 0; i != matrix.length; i++) {
            for (int j = 0; j != matrix[0].length; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }
    }

    public static int[] spiralOrder(int[][] matrix) {
        if (matrix.length == 0) return new int[0];
        int l = 0, r = matrix[0].length - 1, t = 0, b = matrix.length - 1, x = 0;
        int[] res = new int[(r + 1) * (b + 1)];
        while (true) {
            //从左往右
            //列在变，列为循环值
            //从左往右的下一步是往下走，上边界内缩，故++t
            for (int i = l; i <= r; i++) res[x++] = matrix[t][i];
            if (++t > b) break;
            //从上往下，行在变
            //从上往下的下一步是从右往左，右边界收缩，--r
            for (int i = t; i <= b; i++) res[x++] = matrix[i][r];
            if (l > --r) break;
            //从右向左，列在变
            //从右往左的下一步是从下往上，下边界收缩，--b
            for (int i = r; i >= l; i--) res[x++] = matrix[b][i];
            if (t > --b) break;
            //从下到上，行在变
            //从下到上的下一步是从左到右，左边界收缩，++l
            for (int i = b; i >= t; i--) res[x++] = matrix[i][l];
            if (++l > r) break;
        }
        return res;
    }
}