README.md

1411. Number of Ways to Paint N × 3 Grid

You have a grid of size n x 3 and you want to paint each cell of the grid with exactly one of the three colors: Red, Yellow, or Green while making sure that no two adjacent cells have the same color (i.e., no two cells that share vertical or horizontal sides have the same color).

Given n the number of rows of the grid, return the number of ways you can paint this grid. As the answer may grow large, the answer must be computed modulo 109 + 7.

Example 1:

Input: n = 1
Output: 12
Explanation: There are 12 possible way to paint the grid as shown.

Example 2:

Input: n = 5000
Output: 30228214

Constraints:

• n == grid.length
• 1 <= n <= 5000

Solutions (Rust)

1. Solution

impl Solution {
    pub fn num_of_ways(n: i32) -> i32 {
        let mut x = 6;
        let mut y = 6;

        for _ in 1..n {
            x = (x + y) % 1_000_000_007 * 2 % 1_000_000_007;
            y = (x + y) % 1_000_000_007;
        }

        (x + y) % 1_000_000_007
    }
}