一、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.
二、代码分析
import java.util.ArrayList;
public class Solution {
public ArrayList<Integer> printMatrix(int [][] matrix) {
ArrayList<Integer> list = new ArrayList<Integer>();
//数组的行数
int rows = matrix.length;
int columns = matrix[0].length;
if(matrix == null || columns <= 0 || rows <= 0){
return null;
}
int start = 0;
while(columns > start *2 && rows > start * 2){
print1Circle(list,matrix,columns,rows,start);
start++;
}
return list;
}
public void print1Circle(ArrayList<Integer> list, int[][] matrix,int columns, int rows, int start) {
int endX = columns - 1 - start;
int endY = rows - 1 - start;
//从左往右打印一行
for (int i = start; i <= endX; i++) {
list.add(matrix[start][i]);
}
//从上往下打印一列,至少有两行
if (start < endY){
for (int i = start+1; i <= endY; i++) {
list.add(matrix[i][endX]);
}
}
//从右往左打印一行,至少有两行两列
if (start < endY && start < endX){
for (int i = endX - 1; i >= start; i--) {
list.add(matrix[endY][i]);
}
}
//从下往上打印一列,至少有三行两列
if (start < endY -1 && start < endX){
for (int i = endY - 1; i >= start + 1; i--) {
list.add(matrix[i][start]);
}
}
}
}
运行结果: