题目链接

牛客网

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

public class Solution {
   
    public ArrayList<Integer> printMatrix(int [][] matrix) {
   
        ArrayList<Integer> res = new ArrayList<>();
        if (matrix==null || matrix.length==0) return res;
        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++) res.add(matrix[r1][i]);
            for (int i=r1+1;i<=r2;i++) res.add(matrix[i][c2]);
            if (r1 != r2)
                for (int i=c2-1;i>=c1;i--) res.add(matrix[r2][i]);
            if (c1 != c2)
                for (int i=r2-1;i>r1;i--) res.add(matrix[i][c1]);
            r1++; r2--; c1++; c2--;
        }
        return res;
    }
}