Create 212.Word-Search-II.cpp

Trie/212.Word-Search-II/212.Word-Search-II.cpp

@@ -0,0 +1,79 @@
+class Solution {
+    class TrieNode
+    {
+        public:
+        TrieNode* next[26];
+        bool isEnd;
+        TrieNode()
+        {
+            for (int i=0; i<26; i++)
+                next[i]=NULL;
+            isEnd=false;
+        }
+    };
+    TrieNode* root;
+    set<string>Set;
+    int M;
+    int N;
+public:
+    vector<string> findWords(vector<vector<char>>& board, vector<string>& words) 
+    {
+        root=new TrieNode();
+
+        for (int i=0; i<words.size(); i++)
+            build(words[i]);
+
+        M=board.size();
+        N=board[0].size();            
+        auto visited=vector<vector<int>>(M,vector<int>(N,0));
+
+        string word;
+        for (int i=0; i<M; i++)
+         for (int j=0; j<N; j++)
+         {             
+             visited[i][j]=1;
+             DFS(i,j,root,word,visited,board);
+             visited[i][j]=0;
+         }
+
+        vector<string>results(Set.begin(),Set.end());
+        return results;
+    }
+
+    void build(string word)
+    {
+        TrieNode* node=root;
+        for (int i=0; i<word.size(); i++)
+        {
+            char ch=word[i];
+            if (node->next[ch-'a']==NULL)
+                node->next[ch-'a']=new TrieNode();
+            node=node->next[ch-'a'];
+        }
+        node->isEnd=true;
+    }
+
+    void DFS(int i, int j, TrieNode* node, string word, vector<vector<int>>&visited, vector<vector<char>>& board)
+    {
+        if (node->next[board[i][j]-'a']==NULL) return;
+
+        node = node->next[board[i][j]-'a'];
+        word += board[i][j];
+
+        if (node->isEnd==true) Set.insert(word);
+
+        vector<pair<int,int>>dir={{1,0},{-1,0},{0,1},{0,-1}};        
+
+        for (int k=0; k<4; k++)
+        {
+            int x=i+dir[k].first;
+            int y=j+dir[k].second;
+            if (x<0||x>=M||y<0||y>=N) continue;
+            if (visited[x][y]==1) continue;
+
+            visited[x][y]=1;
+            DFS(x,y,node,word,visited,board);
+            visited[x][y]=0;                            
+        }        
+    }
+};