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.

解题思路

• 打印矩阵时，为一圈一圈打印，保证每一行每一列终点均大于等于起点即可。

代码

import java.util.ArrayList;
public class Solution {
    public ArrayList<Integer> printMatrix(int [][] matrix) {
       ArrayList<Integer> 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;
    }
}