212. Word Search II

Author: amitbansal7

word-search-ii.cpp

@@ -0,0 +1,77 @@
+//Runtime: 39 ms
+class Solution {
+public:
+    vector<string>res;
+    struct TrieNode
+    {
+        struct TrieNode* children[26];
+        string word;
+    };
+
+    TrieNode* NewNode()
+    {
+        TrieNode* node = new TrieNode;
+        node->word = "";
+        for(int i=0;i<26;i++)
+            node->children[i] = NULL;
+        return node;
+    }
+
+    struct TrieNode* BuildTrie(vector<string>&words)
+    {
+        struct TrieNode* root = NewNode();
+        for(string word:words)
+        {
+            TrieNode* crawl = root;
+            for(char c:word)
+            {
+                if(crawl->children[c-'a'] == NULL)
+                    crawl->children[c-'a'] = NewNode();
+
+                crawl = crawl->children[c-'a'];
+            }
+            crawl->word = word;
+        }
+
+        return root;
+    }
+
+
+    void solve(vector<vector<char> > &board, int i, int j, struct TrieNode* trie)
+    {
+        char c = board[i][j];
+        if(c == '$' || !trie->children[c-'a'])
+            return;
+
+        trie = trie->children[c-'a'];
+
+        if(trie->word != "")
+        {
+            res.push_back(trie->word);
+            trie->word = "";
+        }
+
+        board[i][j] = '$';
+
+        if(i>0)
+            solve(board, i-1, j, trie);
+        if(i<board.size()-1)
+            solve(board, i+1, j, trie);
+        if(j >0)
+            solve(board, i, j-1, trie);
+
+        if(j<board[0].size() - 1)
+            solve(board, i, j+1, trie);
+
+        board[i][j] = c;
+    }
+
+    vector<string> findWords(vector<vector<char>>& board, vector<string>& words) {
+        struct TrieNode* trie = BuildTrie(words);
+
+        for(int i=0;i<board.size();i++)
+            for(int j=0;j<board[0].size();j++)
+                solve(board, i, j, trie);
+        return res;
+    }
+};