LeetCode in Kotlin

3963. Create Grid With Exactly One Path

Easy

You are given two integers m and n, representing the number of rows and columns of a grid.

Construct any m x n grid consisting only of the characters '.' and '#', where:

• '.' represents a free cell.
• '#' represents an obstacle cell.

A valid path is a sequence of free cells that:

• Starts at the top-left cell (0, 0).
• Ends at the bottom-right cell (m - 1, n - 1).
• Moves only:
  • Right, from (i, j) to (i, j + 1), or
  • Down, from (i, j) to (i + 1, j).

Return any grid such that there is exactly one valid path from the top-left cell to the bottom-right cell.

Example 1:

Input: m = 2, n = 3

Output: [”..#”,”#..”]

Explanation:

The only valid path is: (0,0) → (0,1) → (1,1) → (1,2)

Example 2:

Input: m = 3, n = 3

Output: [”..#”,”#..”,”##.”]

Explanation:

The only valid path is: (0,0) → (0,1) → (1,1) → (1,2) → (2,2)

Example 3:

Input: m = 1, n = 4

Output: [“….”]

Explanation:

The only valid path is: (0,0) → (0,1) → (0,2) → (0,3)

Constraints:

• 1 <= m, n <= 25

Solution

class Solution {
    fun createGrid(m: Int, n: Int): Array<String> {
        val safeN = maxOf(0, n)
        val firstRow = ".".repeat(safeN)
        val subsequentRow = if (n > 0) {
            "#".repeat(maxOf(0, n - 1)) + "."
        } else {
            "".repeat(safeN)
        }
        return Array(m) { i ->
            if (i == 0) firstRow else subsequentRow
        }
    }
}

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