LeetCode in Kotlin

2257. Count Unguarded Cells in the Grid

Medium

You are given two integers m and n representing a 0-indexed m x n grid. You are also given two 2D integer arrays guards and walls where guards[i] = [rowi, coli] and walls[j] = [rowj, colj] represent the positions of the ith guard and jth wall respectively.

A guard can see every cell in the four cardinal directions (north, east, south, or west) starting from their position unless obstructed by a wall or another guard. A cell is guarded if there is at least one guard that can see it.

Return the number of unoccupied cells that are not guarded.

Example 1:

Input: m = 4, n = 6, guards = [[0,0],[1,1],[2,3]], walls = [[0,1],[2,2],[1,4]]

Output: 7

Explanation: The guarded and unguarded cells are shown in red and green respectively in the above diagram. There are a total of 7 unguarded cells, so we return 7.

Example 2:

Input: m = 3, n = 3, guards = [[1,1]], walls = [[0,1],[1,0],[2,1],[1,2]]

Output: 4

Explanation: The unguarded cells are shown in green in the above diagram. There are a total of 4 unguarded cells, so we return 4.

Constraints:

• 1 <= m, n <= 105
• 2 <= m * n <= 105
• 1 <= guards.length, walls.length <= 5 * 104
• 2 <= guards.length + walls.length <= m * n
• guards[i].length == walls[j].length == 2
• 0 <= rowi, rowj < m
• 0 <= coli, colj < n
• All the positions in guards and walls are unique.

Solution

@Suppress("NAME_SHADOWING")
class Solution {
    fun countUnguarded(m: Int, n: Int, guards: Array<IntArray>, walls: Array<IntArray>): Int {
        val matrix = Array(m) { CharArray(n) }
        var result = 0
        for (i in guards.indices) {
            val guardRow = guards[i][0]
            val guardCol = guards[i][1]
            matrix[guardRow][guardCol] = 'G'
        }
        for (i in walls.indices) {
            val wallRow = walls[i][0]
            val wallCol = walls[i][1]
            matrix[wallRow][wallCol] = 'W'
        }
        for (i in guards.indices) {
            var currentRow = guards[i][0]
            var currentCol = guards[i][1] - 1
            extracted(matrix, currentRow, currentCol)
            currentRow = guards[i][0]
            currentCol = guards[i][1] + 1
            extracted(n, matrix, currentRow, currentCol)
            currentRow = guards[i][0] - 1
            currentCol = guards[i][1]
            extracted1(matrix, currentRow, currentCol)
            currentRow = guards[i][0] + 1
            currentCol = guards[i][1]
            extracted1(m, matrix, currentRow, currentCol)
        }
        for (i in 0 until m) {
            for (j in 0 until n) {
                if (matrix[i][j] != 'R' && matrix[i][j] != 'G' && matrix[i][j] != 'W') {
                    result++
                }
            }
        }
        return result
    }

    private fun extracted1(m: Int, matrix: Array<CharArray>, currentRow: Int, currentCol: Int) {
        var currentRow = currentRow
        while (currentRow <= m - 1) {
            if (matrix[currentRow][currentCol] != 'W' && matrix[currentRow][currentCol] != 'G') {
                matrix[currentRow][currentCol] = 'R'
            } else {
                break
            }
            currentRow++
        }
    }

    private fun extracted1(matrix: Array<CharArray>, currentRow: Int, currentCol: Int) {
        var currentRow = currentRow
        while (currentRow >= 0) {
            if (matrix[currentRow][currentCol] != 'W' && matrix[currentRow][currentCol] != 'G') {
                matrix[currentRow][currentCol] = 'R'
            } else {
                break
            }
            currentRow--
        }
    }

    private fun extracted(n: Int, matrix: Array<CharArray>, currentRow: Int, currentCol: Int) {
        var currentCol = currentCol
        while (currentCol <= n - 1) {
            if (matrix[currentRow][currentCol] != 'W' && matrix[currentRow][currentCol] != 'G') {
                matrix[currentRow][currentCol] = 'R'
            } else {
                break
            }
            currentCol++
        }
    }

    private fun extracted(matrix: Array<CharArray>, currentRow: Int, currentCol: Int) {
        var currentCol = currentCol
        while (currentCol >= 0) {
            if (matrix[currentRow][currentCol] != 'W' && matrix[currentRow][currentCol] != 'G') {
                matrix[currentRow][currentCol] = 'R'
            } else {
                break
            }
            currentCol--
        }
    }
}

This site is open source. Improve this page.