剑指offer-题20：顺时针打印矩阵

落日映苍穹つ 2022-05-29 04:58 127阅读 0赞

## **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，如果输入如下矩阵：

则依次打印出数字：1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.

实验平台：[牛客网][Link 1]

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## **解决思路：** ##

![这里写图片描述][70]

![这里写图片描述][70 1]

![这里写图片描述][70 2]

![这里写图片描述][70 3]

java:

import java.util.ArrayList;
    public class Solution {
        ArrayList<Integer> arrayList;
    
    	public ArrayList<Integer> printMatrix(int[][] matrix) {
    		int rows = matrix.length;
    		int cols = matrix[0].length;
    		if (rows == 0 || cols == 0) {
    			return null;
    		}
    		int start = 0;
    		arrayList = new ArrayList<Integer>();
    		while (cols > 2 * start && rows > 2 * start) {
    			printMatrixInCircle(matrix, rows, cols, start);
    			start++;
    		}
    		return arrayList;
    	}
    
    	public void printMatrixInCircle(int[][] matrix, int rows, int cols, int start) {
    		int endX = cols - 1 - start;
    		int endY = rows - 1 - start;
    
    		// 从左到右打印一行
    		for (int i = start; i <= endX; i++) {
    			arrayList.add(new Integer(matrix[start][i]));
    		}
    
    		// 从上到下打印一列
    		if (endY > start) {
    			for (int i = start + 1; i <= endY; i++) {
    				arrayList.add(new Integer(matrix[i][endX]));
    			}
    		}
    
    		// 从右往左打印一行
    		if (endY > start && endX > start) {
    			for (int i = endX - 1; i >= start; i--) {
    				arrayList.add(new Integer(matrix[endY][i]));
    			}
    		}
    
    		// 从下往上打印一列
    		if (endX > start && endY > start + 1) {
    			for (int i = endY - 1; i > start; i--) {
    				arrayList.add(new Integer(matrix[i][start]));
    			}
    
    		}
        }
    }

python:

略

[Link 1]: https://www.nowcoder.com/ta/coding-interviews?page=1
[70]: /images/20220529/d21975aef86447d89d88d85c16c0c5c9.png
[70 1]: /images/20220529/fbd916e68fd243bbb77ad5022af1e880.png
[70 2]: /images/20220529/3516057930124b419d2d4b499d2f222b.png
[70 3]: /images/20220529/e7c50a44d5bc4aa89aa7fc0e39f6ef33.png