LeetCode in Kotlin

1001. Grid Illumination

Hard

There is a 2D grid of size n x n where each cell of this grid has a lamp that is initially turned off.

You are given a 2D array of lamp positions lamps, where lamps[i] = [rowi, coli] indicates that the lamp at grid[rowi][coli] is turned on. Even if the same lamp is listed more than once, it is turned on.

When a lamp is turned on, it illuminates its cell and all other cells in the same row, column, or diagonal.

You are also given another 2D array queries, where queries[j] = [rowj, colj]. For the jth query, determine whether grid[rowj][colj] is illuminated or not. After answering the jth query, turn off the lamp at grid[rowj][colj] and its 8 adjacent lamps if they exist. A lamp is adjacent if its cell shares either a side or corner with grid[rowj][colj].

Return an array of integers ans, where ans[j] should be 1 if the cell in the jth query was illuminated, or 0 if the lamp was not.

Example 1:

Input: n = 5, lamps = [[0,0],[4,4]], queries = [[1,1],[1,0]]

Output: [1,0]

Explanation: We have the initial grid with all lamps turned off. In the above picture we see the grid after turning on the lamp at grid[0][0] then turning on the lamp at grid[4][4]. The 0^th query asks if the lamp at grid[1][1] is illuminated or not (the blue square). It is illuminated, so set ans[0] = 1. Then, we turn off all lamps in the red square. The 1^st query asks if the lamp at grid[1][0] is illuminated or not (the blue square). It is not illuminated, so set ans[1] = 0. Then, we turn off all lamps in the red rectangle.

Example 2:

Input: n = 5, lamps = [[0,0],[4,4]], queries = [[1,1],[1,1]]

Output: [1,1]

Example 3:

Input: n = 5, lamps = [[0,0],[0,4]], queries = [[0,4],[0,1],[1,4]]

Output: [1,1,0]

Constraints:

• 1 <= n <= 109
• 0 <= lamps.length <= 20000
• 0 <= queries.length <= 20000
• lamps[i].length == 2
• 0 <= rowi, coli < n
• queries[j].length == 2
• 0 <= rowj, colj < n

Solution

class Solution {
    fun gridIllumination(n: Int, lamps: Array<IntArray>, queries: Array<IntArray>): IntArray {
        val rowIlluminations: MutableMap<Int, Int> = HashMap()
        val colIlluminations: MutableMap<Int, Int> = HashMap()
        val posDiagIlluminations: MutableMap<Int, Int> = HashMap()
        val negDiagIlluminations: MutableMap<Int, Int> = HashMap()
        val lampPlacements: MutableSet<Long> = HashSet()
        for (lamp in lamps) {
            val row = lamp[0]
            val col = lamp[1]
            var key = row.toLong()
            key = key * n + col
            if (lampPlacements.contains(key)) {
                continue
            }
            incr(rowIlluminations, row)
            incr(colIlluminations, col)
            incr(posDiagIlluminations, row + col)
            incr(negDiagIlluminations, row + (n - 1 - col))
            lampPlacements.add(key)
        }
        val ans = IntArray(queries.size)
        for (i in ans.indices) {
            val row = queries[i][0]
            val col = queries[i][1]
            if (rowIlluminations.containsKey(row) ||
                colIlluminations.containsKey(col) ||
                posDiagIlluminations.containsKey(row + col) ||
                negDiagIlluminations.containsKey(row + (n - 1 - col))
            ) {
                ans[i] = 1
            }
            val topRow = 0.coerceAtLeast(row - 1)
            val bottomRow = (n - 1).coerceAtMost(row + 1)
            val leftCol = 0.coerceAtLeast(col - 1)
            val rightCol = (n - 1).coerceAtMost(col + 1)
            for (r in topRow..bottomRow) {
                for (c in leftCol..rightCol) {
                    var key = r.toLong()
                    key = key * n + c
                    if (lampPlacements.contains(key)) {
                        decr(rowIlluminations, r)
                        decr(colIlluminations, c)
                        decr(posDiagIlluminations, r + c)
                        decr(negDiagIlluminations, r + (n - 1 - c))
                        lampPlacements.remove(key)
                    }
                }
            }
        }
        return ans
    }

    private fun incr(map: MutableMap<Int, Int>, key: Int) {
        map[key] = map.getOrDefault(key, 0) + 1
    }

    private fun decr(map: MutableMap<Int, Int>, key: Int) {
        val v = map.getValue(key)
        if (map[key] == 1) {
            map.remove(key)
        } else {
            map[key] = v - 1
        }
    }
}

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