【剑指offer】19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.
*/

import java.util.ArrayList;
public class Solution {

//每次打印第一行，然后删除第一行并逆时针转动
public ArrayList<Integer> printMatrix(int [][] matrix) {
if(null==matrix)
return null;

ArrayList<Integer> list = new ArrayList<>();
int row = matrix.length;
//循环代替递归
while (row != 0) {
for (int i = 0; i < matrix[0].length; i++) {
list.add(matrix[0][i]);
}
if (row == 1)
break;
matrix = turn(matrix);
row = matrix.length;
}
return list;
}

//数组逆时针旋转90°
private int[][] turn(int[][] matrix) {

int col = matrix[0].length;
int row = matrix.length;
int[][] newMatrix = new int[col][row - 1];
for (int j = col - 1; j >= 0; j--) {
for (int i = 1; i < row; i++) {
newMatrix[col-j-1][i-1] = matrix[i][j];
}
}
return newMatrix;
}

public static void main(String[] args) {
Solution s=new Solution();

int [][] matrix={{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16}};
ArrayList<Integer> list =s.printMatrix(matrix);

for (int i:list)
System.out.print(i+" ");
}
}