JZ-019-顺时针打印矩阵 java算法矩阵

顺时针打印矩阵题目描述

【JZ-019-顺时针打印矩阵】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: 顺时针打印矩阵

代码

import java.util.ArrayList; /** * 标题：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?tpId=13&&tqId=11172&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking */ public class Jz19 {public ArrayList printMatrix2(int[][] matrix) { ArrayList list = new ArrayList<>(); if (matrix == null || matrix.length == 0 || matrix[0].length == 0) { return list; } int up = 0; int down = matrix.length - 1; int left = 0; int right = matrix[0].length - 1; while (true) { // 最上面一行 for (int col = left; col <= right; col++) { list.add(matrix[up][col]); } // 向下逼近 up++; // 判断是否越界 if (up > down) { break; } // 最右边一行 for (int row = up; row <= down; row++) { list.add(matrix[row][right]); } // 向左逼近 right--; // 判断是否越界 if (left > right) { break; } // 最下面一行 for (int col = right; col >= left; col--) { list.add(matrix[down][col]); } // 向上逼近 down--; // 判断是否越界 if (up > down) { break; } // 最左边一行 for (int row = down; row >= up; row--) { list.add(matrix[row][left]); } // 向右逼近 left++; // 判断是否越界 if (left > right) { break; } } return list; }public ArrayList printMatrix(int[][] matrix) { ArrayList result = new ArrayList(); int r1 = 0, r2 = matrix.length - 1, c1 = 0, c2 = matrix[0].length - 1; while (r1 <= r2 && c1 <= c2) { for (int i = c1; i <= c2; i++) { result.add(matrix[r1][i]); } for (int i = r1 + 1; i <= r2; i++) { result.add(matrix[i][c2]); } if (r1 != r2) { for (int i = c2 - 1; i >= c1; i--) { result.add(matrix[r2][i]); } } if (c1 != c2) { for (int i = r2 - 1; i > r1; i--) { result.add(matrix[i][c1]); } } r1++; r2--; c1++; c2--; } return result; } }