剑指offer——第十九题：顺时针打印矩阵

最新推荐文章于 2025-07-14 00:23:50 发布

原创最新推荐文章于 2025-07-14 00:23:50 发布 · 219 阅读

0 ·

CC 4.0 BY-SA版权

剑指offer 专栏收录该内容

64 篇文章

订阅专栏

本文介绍了一种矩阵螺旋打印算法，包括非递归和递归两种实现方式，详细展示了如何按顺时针方向从外向内打印矩阵中的数字，适用于4X4及任意大小的矩阵。

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.

提示：编写代码时，可以先不考虑单行或者单列的情况，等编写完成后，再假设此时是单行（列），然后走一遍程序，根据哪里会出问题来修改解决单行（列）情况。

非递归版

import java.util.ArrayList;

public class s {
    public ArrayList<Integer> printMatrix(int[][] matrix) {

        ArrayList<Integer> list = new ArrayList<>();
        int index = 0; //圈数
        int row = matrix.length;
        int col = matrix[0].length;

        int left = 0;
        int right = col - 1;
        int top = 0;
        int bottom = row - 1;

        while (left <= right && top <= bottom) {
            for (int i = left; i <= right; i++) {
                list.add(matrix[top][i]);
            }

            for (int i = top + 1; i <= bottom; i++) {
                list.add(matrix[i][right]);
            }

            if (top != bottom) {
                for (int i = right - 1; i >= left; i--) {
                    list.add(matrix[bottom][i]);
                }
            }

            if (left != right) {
                for (int i = bottom - 1; i >= top + 1; i--) {
                    list.add(matrix[i][left]);
                }
            }

            left++;
            right--;
            top++;
            bottom--;
            index++;
        }
        System.out.println(index);
        return list;
    }

    public static void main(String[] args) {
        int[][] matrix = {{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}, {11, 12, 13, 14, 15},
                {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25}};
        s t = new s();
        ArrayList<Integer> res = t.printMatrix(matrix);
        System.out.println(res); //其中圈数index为3
    }
}

递归版

public class T_19_PrintMatrix {

    public ArrayList<Integer> printMatrix(int[][] matrix) {
        int tR = 0;
        int tC = 0;
        int dR = matrix.length - 1;
        int dC = matrix[0].length - 1;

        ArrayList<Integer> list = new ArrayList<>();
        while (tR <= dR && tC <= dC) {
            list = printEdge(matrix, tR++, tC++, dR--, dC--, list);
        }
        return list;
    }

    public static ArrayList<Integer> printEdge(int[][] m, int tR, int tC, int dR, int dC, ArrayList list) {
        if (tR == dR) {
            for (int i = tC; i <= dC; i++) {
                list.add(m[tR][i]);
            }
        } else if (tC == dC) {
            for (int i = tR; i <= dR; i++) {
                list.add(m[i][tC]);
            }
        } else {
            int curC = tC;
            int curR = tR;
            while (curC != dC) {
                list.add(m[tR][curC]);
                curC++;
            }
            while (curR != dR) {
                list.add(m[curR][dC]);
                curR++;
            }
            while (curC != tC) {
                list.add(m[dR][curC]);
                curC--;
            }
            while (curR != tR) {
                list.add(m[curR][tC]);
                curR--;
            }
        }
        return list;
    }

    public static void main(String[] args) {
        int[][] matrix = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12},
                {13, 14, 15, 16}};
        T_19_PrintMatrix t = new T_19_PrintMatrix();
        ArrayList<Integer> res = t.printMatrix(matrix);
        System.out.println(res);
    }
}