牛客题霸NC31转圈打印矩阵Java题解

牛客题霸NC31转圈打印矩阵Java题解
https://www.nowcoder.com/practice/fe219d47475842e68e64ba6fea42b846?tpId=117&&tqId=35276&rp=1&ru=/ta/job-code-high&qru=/ta/job-code-high/question-ranking
方法：逐个遍历
解题思路：按照从左到右、从上到下、从右到左、从下到上的顺序依此遍历。

import java.util.*;


public class Solution {
    /**
     * 
     * @param matrix int整型二维数组 the matrix
     * @return int整型一维数组
     */
    public int[] printMatrix (int[][] matrix) {
           if(matrix.length == 0) {
             return null;
        }

        int left = 0; 
        int right = matrix[0].length - 1;
        int top = 0;
        int bottom = matrix.length - 1; 
        int x = 0;

        int[] res = new int[(right + 1) * (bottom + 1)];

        while(true) {
            for(int i = left; i <= right; i++) {  //从左到右
                res[x++] = matrix[top][i]; 
            }

            if(++top > bottom){
                break;
            } 
            for(int i = top; i <= bottom; i++){  // 从上到下
                res[x++] = matrix[i][right]; 
            } 

            if(left > --right){
                break;
            } 
            for(int i = right; i >= left; i--){  //从右到左
                 res[x++] = matrix[bottom][i]; 
            } 

            if(top > --bottom){
                break;
            }
            for(int i = bottom; i >= top; i--){  //从下到上
                res[x++] = matrix[i][left];
            } 

            if(++left > right){
               break;
            } 
        }
        return res;
    }
}