笔试题：蛇形矩阵

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n = 2时

[1, 2]
[4, 3]

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n = 3 时

[1, 2, 3]
[8, 9, 4]
[7, 6, 5]

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n = 4 时

[1,   2,    3,   4, 5]
[16, 17, 18, 19, 6]
[15, 24, 25, 20, 7]
[14, 23, 22, 21, 8]
[13, 12, 11, 10, 9]

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思路：先打印最外层一圈，缩小问题，再打印内层一圈，依此类推

package test5;

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int num = scan.nextInt();
        int[][] res = new int[num][num];
        int row = 0;
        int col = 0;
        int count = 1;
        int end = num;
        int i = row;
        int j = col;
        while (count <= num * num) {
            // 打印最上一行
            for (i = row, j = col; j < end; j++) {
                res[i][j] = count++;
            }

            // //打印最右一列
            for (i = i + 1, j = j - 1; i < end; i++) {
                res[i][j] = count++;
            }

            // //打印最下一行
            for (j = j - 1, i = i - 1; j >= (num - end); j--) {
                res[i][j] = count++;
            }

            // //打印最左一列
            for (i = i - 1, j = j + 1; i > (num - end); i--) {
                res[i][j] = count++;
            }
            //行列增1
             row ++;
             col ++;
             end --;
        }
        for (int k = 0; k < num; k++) {
            System.out.println(Arrays.toString(res[k]));
        }
    }
}