snake

package com.company;
import java.util.Scanner;

class Main {
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int[][] arr;
        arr = new int[N][N];
        int x;
        int y;
        int value = 1;
        for (int i = 0; i < N; i++) {
            if (i % 2 == 0) {
                x = 0;
                y = i;
                while (y >= 0) {
                    arr[x][y] = value;
                    value++;
                    x++;
                    y--;
                }
            } else {
                x = i;
                y = 0;
                while (x >= 0) {
                    arr[x][y] = value;
                    value++;
                    x--;
                    y++;
                }

            }
        }
        for (int i = 1; i < N; i++) {
            if (i % 2 == 0) {
                x = N - 1;
                y = i;
                while (y <= N - 1) {
                    arr[x][y] = value;
                    value++;
                    x--;
                    y++;
                }
            } else {
                x = i;
                y = N - 1;
                while (x <= N - 1) {
                    arr[x][y] = value;
                    value++;
                    x++;
                    y--;
                }
            }
        }
        for (int i = 0; i < N; i++){
            for(int j = 0; j < N; j++){
                System.out.print(arr[i][j] + " ");
            }
            System.out.println();
        }
    }
}