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 {
public ArrayList<Integer> printMatrix(int [][] matrix) {
if(matrix == null)
return null;
ArrayList<Integer> list = new ArrayList<>();
int row = matrix.length;
int col = matrix[0].length;
int left = 0, top = 0, right = col-1, bottom = row-1;
while(left <= right && top <= bottom)
{
//从左到右
for(int i = left; i <= right; i++)
{
list.add(matrix[top][i]);
}
//从上到下
for(int j = top+1; j <= bottom; j++)
{
list.add(matrix[j][right]);
}
//从右到左
if(top != bottom)
{
for(int k = right-1; k >= left; k--)
{
list.add(matrix[bottom][k]);
}
}
//从下到上
if(left != right)
{
for(int l = bottom-1; l > top; l--)//注意边界
{
list.add(matrix[l][left]);
}
}
//内圈
top++;
left++;
right--;
bottom--;
}
return list;
}
}