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.
import java.util.ArrayList;
public class Solution {
public ArrayList<Integer> printMatrix(int [][] matrix) {
ArrayList<Integer> res = new ArrayList<>();
if (matrix == null) {
return res;
}
int up = 0,down = matrix.length-1,left = 0,right = matrix[0].length-1;
while(true){
for(int col = left;col<=right;col++){
res.add(matrix[up][col]);
}
up++;//向下逼近
if(up>down){break;}
for(int row = up;row<=down;row++){
res.add(matrix[row][right]);
}
//向左逼近
right--;
if(left>right){ break; }
for(int col = right;col>=left;col--){
res.add(matrix[down][col]);
}
down--;//向上逼近
if(up>down){break;}
for(int row = down;row>=up;row--){
res.add(matrix[row][left]);
}
left++;//向右逼近
if(left>right){break;}
}
return res;
}
}