LeetCode in Kotlin

2018. Check if Word Can Be Placed In Crossword

Medium

You are given an m x n matrix board, representing the current state of a crossword puzzle. The crossword contains lowercase English letters (from solved words), ' ' to represent any empty cells, and '#' to represent any blocked cells.

A word can be placed horizontally (left to right or right to left) or vertically (top to bottom or bottom to top) in the board if:

• It does not occupy a cell containing the character '#'.
• The cell each letter is placed in must either be ' ' (empty) or match the letter already on the board.
• There must not be any empty cells ' ' or other lowercase letters directly left or right of the word if the word was placed horizontally.
• There must not be any empty cells ' ' or other lowercase letters directly above or below the word if the word was placed vertically.

Given a string word, return true if word can be placed in board, or false otherwise.

Example 1:

Input: board = [[”#”, “ “, “#”], [” “, “ “, “#”], [”#”, “c”, “ “]], word = “abc”

Output: true

Explanation: The word “abc” can be placed as shown above (top to bottom).

Example 2:

Input: board = [[” “, “#”, “a”], [” “, “#”, “c”], [” “, “#”, “a”]], word = “ac”

Output: false

Explanation: It is impossible to place the word because there will always be a space/letter above or below it.

Example 3:

Input: board = [[”#”, “ “, “#”], [” “, “ “, “#”], [”#”, “ “, “c”]], word = “ca”

Output: true

Explanation: The word “ca” can be placed as shown above (right to left).

Constraints:

• m == board.length
• n == board[i].length
• 1 <= m * n <= 2 * 105
• board[i][j] will be ' ', '#', or a lowercase English letter.
• 1 <= word.length <= max(m, n)
• word will contain only lowercase English letters.

Solution

class Solution {
    fun placeWordInCrossword(board: Array<CharArray>, word: String): Boolean {
        val m = board.size
        val n = board[0].size
        for (i in 0 until m) {
            for (j in 0 until n) {
                if ((board[i][j] == ' ' || board[i][j] == word[0]) &&
                    (
                        canPlaceTopDown(word, board, i, j) ||
                            canPlaceLeftRight(word, board, i, j) ||
                            canPlaceBottomUp(word, board, i, j) ||
                            canPlaceRightLeft(word, board, i, j)
                        )
                ) {
                    return true
                }
            }
        }
        return false
    }

    private fun canPlaceRightLeft(word: String, board: Array<CharArray>, row: Int, col: Int): Boolean {
        if (col + 1 < board[0].size &&
            (Character.isLowerCase(board[row][col + 1]) || board[row][col + 1] == ' ')
        ) {
            return false
        }
        var k = 0
        var j = col
        while (j >= 0 && k < word.length) {
            if (board[row][j] != word[k] && board[row][j] != ' ') {
                return false
            } else {
                k++
            }
            j--
        }
        return k == word.length && (j < 0 || board[row][j] == '#')
    }

    private fun canPlaceBottomUp(word: String, board: Array<CharArray>, row: Int, col: Int): Boolean {
        if (row + 1 < board.size &&
            (Character.isLowerCase(board[row + 1][col]) || board[row + 1][col] == ' ')
        ) {
            return false
        }
        var k = 0
        var i = row
        while (i >= 0 && k < word.length) {
            if (board[i][col] != word[k] && board[i][col] != ' ') {
                return false
            } else {
                k++
            }
            i--
        }
        return k == word.length && (i < 0 || board[i][col] == '#')
    }

    private fun canPlaceLeftRight(word: String, board: Array<CharArray>, row: Int, col: Int): Boolean {
        if (col > 0 && (Character.isLowerCase(board[row][col - 1]) || board[row][col - 1] == ' ')) {
            return false
        }
        var k = 0
        var j = col
        while (j < board[0].size && k < word.length) {
            if (board[row][j] != word[k] && board[row][j] != ' ') {
                return false
            } else {
                k++
            }
            j++
        }
        return k == word.length && (j == board[0].size || board[row][j] == '#')
    }

    private fun canPlaceTopDown(word: String, board: Array<CharArray>, row: Int, col: Int): Boolean {
        if (row > 0 && (Character.isLowerCase(board[row - 1][col]) || board[row - 1][col] == ' ')) {
            return false
        }
        var k = 0
        var i = row
        while (i < board.size && k < word.length) {
            if (board[i][col] != word[k] && board[i][col] != ' ') {
                return false
            } else {
                k++
            }
            i++
        }
        return k == word.length && (i == board.size || board[i][col] == '#')
    }
}

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