Snail

Snail Sort

Given an n x n array, return the array elements arranged from outermost elements to the middle element, traveling clockwise.

array = [[1,2,3],
         [4,5,6],
         [7,8,9]]
snail(array) #=> [1,2,3,6,9,8,7,4,5]

For better understanding, please follow the numbers of the next array consecutively:

array = [[1,2,3],
         [8,9,4],
         [7,6,5]]
snail(array) #=> [1,2,3,4,5,6,7,8,9]

This image will illustrate things more clearly:

NOTE: The idea is not sort the elements from the lowest value to the highest; the idea is to traverse the 2-d array in a clockwise snailshell pattern.

大意：图片很明显了，顺时针依次向内层输出矩阵的数值

分析：嗯也没什么可想的，直接一层一层向内输出即可，矩阵的下标处理需要仔细一些

附上代码：

import java.util.ArrayList;
import java.util.Arrays;

public class Snail {
    public static int[] snail(int[][] array) {
        // enjoy
        ArrayList<Integer> list = new ArrayList<>();
        int n = 0;
        int row = array.length;
        int col = array[0].length;
        while (n <= array.length / 2){
            for (int i = n;i < col - n;i++)
            {
                list.add(array[n][i]);
            }
            for (int i = n + 1;i < row - n;i++){
                list.add(array[i][col - n - 1]);
            }
            for (int i = col - n - 2;i >= n;i--){
                list.add(array[row - n -1][i]);
            }
            for (int i = row - n -2;i > n;i--){
                list.add(array[i][n]);
            }
            n++;
        }
        //while(n < )
        return list.stream().mapToInt(e -> e).toArray();
    }
}