print matrix clockwise
Question:
Input a matrix and print each number in clockwise order from outside to inside. For example, if you enter the following 4 X 4 matrix: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 then Print out the numbers 1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.
Code:
package com.sjsq.test;
/**
* @author shuijianshiqing
* @date 2020/5/21 22:43
*/
/**
* 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.
*/
import java.util.ArrayList;
public class Solution {
public ArrayList<Integer> printMatrix(int [][] matrix) {
ArrayList<Integer> list = new ArrayList<>();
if(matrix == null || matrix.length == 0 || matrix[0].length == 0){
return list;
}
int up = 0;
int down = matrix.length - 1;
int left = 0;
int right = matrix[0].length - 1;
while(true){
// 最上面一行
for(int col = left;col <= right;col++){
list.add(matrix[up][col]);
}
// 向下逼近
up++;
if(up > down){
break;
}
// 最右边一行
for(int row=up;row<=down;row++){
list.add(matrix[row][right]);
}
// 向左逼近
right--;
if(left>right){
break;
}
// 最下边一行
for(int col=right;col>=left;col--){
list.add(matrix[down][col]);
}
// 向上逼近
down--;
if(up>down){
break;
}
// 最左边一行
for(int row=down;row>=up;row--){
list.add(matrix[row][left]);
}
// 向右逼近
left++;
if(left>right){
break;
}
}
return list;
}
}