Word Search II solution

Author: PDKhan

word-search-ii/PDKhan.cpp

@@ -0,0 +1,65 @@
+class TrieNode{
+public:
+    TrieNode* children[26] = {};
+    string word = "";
+};
+
+class Solution {
+public:
+    void insert(TrieNode* root, const string& word){
+        TrieNode* node = root;
+
+        for(int i = 0; i < word.length(); i++){
+            int idx = word[i] - 'a';
+
+            if(!node->children[idx])
+                node->children[idx] = new TrieNode();
+            
+            node = node->children[idx];
+        }
+        node->word = word;
+    }
+
+    void dfs(int r, int c, vector<vector<char>>& board, TrieNode* root, vector<string>& result){
+        if(r < 0 || r >= board.size() || c < 0 || c >= board[r].size())
+            return;
+
+        char ch = board[r][c];
+
+        if(ch == '#' || !root->children[ch - 'a'])
+            return;
+        
+        root = root->children[ch - 'a'];
+
+        if(!root->word.empty()){
+            result.push_back(root->word);
+            root->word.clear();
+        }
+
+        board[r][c] = '#';
+        
+        dfs(r - 1, c, board, root, result);
+        dfs(r + 1, c, board, root, result);
+        dfs(r, c - 1, board, root, result);
+        dfs(r, c + 1, board, root, result);
+        
+        board[r][c] = ch;
+    }
+
+    vector<string> findWords(vector<vector<char>>& board, vector<string>& words) {
+        TrieNode* root = new TrieNode();
+
+        for(int i = 0; i < words.size(); i++)
+            insert(root, words[i]);
+        
+        vector<string> result;
+
+        for(int i = 0; i < board.size(); i++){
+            for(int j = 0; j < board[i].size(); j++){
+                dfs(i, j, board, root, result);
+            }
+        }
+
+        return result;
+    }
+};