1-6

class Solution {
    public int finalPositionOfSnake(int n, List<String> commands) {
        int number = 0;
        for (String command : commands) {
            if (command.equals("UP")) {
                number -= n;
            } else if (command.equals("DOWN")) {
                number += n;
            } else if (command.equals("RIGHT")) {
                number++;
            } else if (command.equals("LEFT")) {
                number--;
            }
        }
        return number;

        // row = 0, col = 0..2 => indices 0..2 (indices start from 3 * row = 3 * 0 = 0)
        // row = 1, col = 0..2 => indices 3..5 (indices start from 3 * row = 3 * 0 = 0)
        // row = 2, col = 0..2 => indices 6..8 (indices start from 3 * row = 3 * 0 = 0)

        // row =   0, col = 0..n-1 => indices       0 ..  n-1
        // row =   1, col = 0..n-1 => indices       n .. 2n-1
        // row =   2, col = 0..n-1 => indices      2n .. 3n-1
        // ...
        // row = n-1, col = 0..n-1 => indices (n-1)*n .. (n*n)-1

        // 0-th row, 0-th col       => 0
        // 0-th row, 1-st col       => 1
        // 0-th row, 2-nd col       => 2
        // 0-th row, 3-rd col       => 3
        // ...
        // 0-th row, (n - 1)-th col => n - 1

        // 1-st row, 0-th col       => n
        // 1-st row, 1-st col       => n + 1
        // 1-st row, 2-nd col       => n + 2
        // 1-st row, 3-rd col       => n + 3
        // ...
        // 1-st row, (n - 1)-th col => 2 * n - 1

        // ...

        // (n - 1)-th row, 0-th col       => (n - 1) * n
        // (n - 1)-th row, 1-st col       => (n - 1) * n + 1
        // ...
        // (n - 1)-th row, (n - 1)-th col => n * n - 1
    }
}




class Solution {
    public int finalPositionOfSnake(int n, List<String> commands) {
        int row = 0;
        int col = 0;
        for (String command : commands) {
            if (command.equals("UP")) {
                row--;
            } else if (command.equals("DOWN")) {
                row++;
            } else if (command.equals("RIGHT")) {
                col++;
            } else if (command.equals("LEFT")) {
                col--;
            }
        }
        return row * n + col;

        // row = 0, col = 0..2 => indices 0..2 (indices start from 3 * row = 3 * 0 = 0)
        // row = 1, col = 0..2 => indices 3..5 (indices start from 3 * row = 3 * 0 = 0)
        // row = 2, col = 0..2 => indices 6..8 (indices start from 3 * row = 3 * 0 = 0)

        // row =   0, col = 0..n-1 => indices       0 ..  n-1
        // row =   1, col = 0..n-1 => indices       n .. 2n-1
        // row =   2, col = 0..n-1 => indices      2n .. 3n-1
        // ...
        // row = n-1, col = 0..n-1 => indices (n-1)*n .. (n*n)-1

        // 0-th row, 0-th col       => 0
        // 0-th row, 1-st col       => 1
        // 0-th row, 2-nd col       => 2
        // 0-th row, 3-rd col       => 3
        // ...
        // 0-th row, (n - 1)-th col => n - 1

        // 1-st row, 0-th col       => n
        // 1-st row, 1-st col       => n + 1
        // 1-st row, 2-nd col       => n + 2
        // 1-st row, 3-rd col       => n + 3
        // ...
        // 1-st row, (n - 1)-th col => 2 * n - 1

        // ...

        // (n - 1)-th row, 0-th col       => (n - 1) * n
        // (n - 1)-th row, 1-st col       => (n - 1) * n + 1
        // ...
        // (n - 1)-th row, (n - 1)-th col => n * n - 1
    }
}