LeetCode/kt/minimum-obstacle-removal-to-reach-corner.kt

class Solution {
    private data class Position(val x: Int, val y: Int) {
        operator fun plus(rhs: Position): Position = Position(x + rhs.x, y + rhs.y)
    }

    companion object {
        private val DIRECTIONS =
            listOf(
                Position(0, 1),
                Position(0, -1),
                Position(1, 0),
                Position(-1, 0),
            )
    }

    private fun isValid(
        grid: Array<IntArray>,
        p: Position,
    ): Boolean =
        (
            p.y >= 0 && p.y < grid.size && p.x >= 0 && p.x < grid[p.y].size
        )

    fun minimumObstacles(grid: Array<IntArray>): Int {
        val (rows, cols) = grid.size to grid[0].size

        val dp = Array(rows) { IntArray(cols) { Int.MAX_VALUE } }
        dp[0][0] = 0

        val deque = ArrayDeque<Pair<Position, Int>>()
        deque.addLast(Position(0, 0) to 0)

        while (!deque.isEmpty()) {
            val (position, obstacles) = deque.removeFirst()

            DIRECTIONS.forEach { dir ->
                val next = position + dir
                if (!isValid(grid, next) || dp[next.y][next.x] != Int.MAX_VALUE) {
                    return@forEach
                }

                if (grid[next.y][next.x] == 1) {
                    dp[next.y][next.x] = obstacles + 1
                    deque.addLast(next to obstacles + 1)
                } else {
                    dp[next.y][next.x] = obstacles
                    deque.addFirst(next to obstacles)
                }
            }
        }

        return dp[rows - 1][cols - 1]
    }
}