A function to search words in a 2D character matrix

WordSearch.swift

import Foundation

func find(word: String, in arr: [[Character]]) -> Bool {
    let word = Array(word)

    var index = 0

    func check(x: Int, y: Int) -> Bool {
        // check bounds
        guard x >= 0,
              y >= 0,
              x < arr[0].count,
              y < arr.count, index < word.endIndex
        else { return false }

        // check if matches
        return word[index] == arr[x][y]
    }

    func checkAll(x: Int, y: Int, modifies: [((inout Int, inout Int) -> Void)]) -> Bool {
        guard check(x: x, y: y) else { return false }
        for modify in modifies {
            index = 0
            var x = x
            var y = y
            // perform transformation and
            // keep performing transformation if it's good
            repeat {
                index += 1
                modify(&x, &y)
            } while check(x: x, y: y)

            // check if the word has been completed
            if index == word.endIndex { return true }
        }
        return false
    }

    // array of transformations, directions to search
    let operations: [(inout Int, inout Int) -> Void] = [
        { x, y in x -= 1; y -= 1 },
        { x, y in x -= 0; y -= 1 },
        { x, y in x += 1; y -= 1 },
        { x, y in x -= 1; y -= 0 },
        // identity transformation ignored:
        // { x, y in x -= 0; y -= 0 },
        { x, y in x += 1; y -= 0 },
        { x, y in x -= 1; y += 1 },
        { x, y in x -= 0; y += 1 },
        { x, y in x += 1; y += 1 },
    ]

    for y in 0 ..< arr.count {
        for x in 0 ..< arr[0].count {
            if checkAll(x: x, y: y, modifies: operations) {
                return true
            }
            index = 0
        }
    }
    return false
}

let arr: [[Character]] = [
    ["A", "L", "U", "D"],
    ["C", "O", "B", "E"],
    ["N", "E", "E", "D"],
    ["H", "B", "R", "E"],
]

print(find(word: "UBER", in: arr) == true)
print(find(word: "ALUD", in: arr) == true)
print(find(word: "COBE", in: arr) == true)
print(find(word: "NEED", in: arr) == true)
print(find(word: "ACNH", in: arr) == true)
print(find(word: "DEDE", in: arr) == true)
print(find(word: "AOEE", in: arr) == true)
print(find(word: "DBEH", in: arr) == true)
print(find(word: "EEOA", in: arr) == true)

print(find(word: "BER", in: arr) == true)
print(find(word: "LUD", in: arr) == true)
print(find(word: "OBE", in: arr) == true)
print(find(word: "EED", in: arr) == true)
print(find(word: "CNH", in: arr) == true)
print(find(word: "EDE", in: arr) == true)
print(find(word: "OEE", in: arr) == true)
print(find(word: "BEH", in: arr) == true)
print(find(word: "EOA", in: arr) == true)

print(find(word: "AONB", in: arr) == false)
print(find(word: "BED", in: arr) == false)
print(find(word: "LUBER", in: arr) == false)
print(find(word: "DEER", in: arr) == false)
print(find(word: "BEEB", in: arr) == false)
print(find(word: "HEED", in: arr) == false)
print(find(word: "EEOL", in: arr) == false)
print(find(word: "RDEE", in: arr) == false)
print(find(word: "EDEB", in: arr) == false)