Merge pull request neetcode-gh#1297 from fomagran/trie

Create 212-Word-Search-II.swift

Author: Ahmad-A0

swift/212-Word-Search-II.swift

@@ -0,0 +1,69 @@
+/**
+ * Question Link: https://leetcode.com/problems/word-search-ii/
+ */
+
+class Solution {
+    class TrieNode {
+        var children =  [Character: TrieNode]()
+        var word: String = ""
+    }
+
+    func findWords(_ board: [[Character]], _ words: [String]) -> [String] {
+        var answer = [String]()
+        let root = buildTrie(words)
+    
+        var board = board
+    
+        for row in 0..<board.count {
+            for col in 0..<board[0].count {
+                if root.children[board[row][col]] != nil {
+                    dfs(row, col, root,&board,&answer)
+                }
+            }
+        }
+
+        return answer
+    }
+
+    func buildTrie(_ words: [String]) -> TrieNode {
+        let root = TrieNode()
+        for word in words {
+            var current = root
+
+            word.forEach {
+                if current.children[$0] == nil {
+                    current.children[$0] = TrieNode()
+                }
+                current = current.children[$0]!
+            }
+            current.word = word
+        }
+
+         return root
+    }
+
+     func getInBoardChild(_ x: Int, _ y: Int,_ board:[[Character]],_ root: TrieNode) -> TrieNode? {
+        if 0..<board[0].count ~= x && 0..<board.count ~= y && board[y][x] != "." {
+            return root.children[board[y][x]]
+        }
+        return nil
+    }
+    
+    func dfs( _ y: Int,_ x: Int,_ root: TrieNode,_ board: inout [[Character]],_ answer: inout [String]) {
+        guard let child = getInBoardChild(x, y, board, root) else { return }
+
+        let char = board[y][x]
+        board[y][x] = "."
+
+        if !child.word.isEmpty {
+            answer.append(child.word)
+            child.word = ""
+        }
+
+        for d in [(x-1,y),(x+1,y),(x,y-1),(x,y+1)] {
+            dfs(d.1,d.0, child,&board,&answer)
+        }
+
+         board[y][x] = char
+    }
+}