Create 139.Word-Break_Trie.cpp

Trie/139.Word-Break/139.Word-Break_Trie.cpp

@@ -0,0 +1,59 @@
+class Solution {
+    class TrieNode
+    {
+        public:
+        TrieNode* next[26];
+        bool end;
+        TrieNode()
+        {
+            end = false;
+            for (int i=0;i<26;i++)
+                next[i] = NULL;
+        }
+    };
+    TrieNode* root;
+    int memo[300];
+public:
+    bool wordBreak(string s, vector<string>& wordDict) 
+    {
+        root = new TrieNode();
+        for (auto word: wordDict)
+        {
+            TrieNode* node = root;
+            for (auto ch: word)
+            {
+                if (node->next[ch-'a']==NULL)
+                    node->next[ch-'a'] = new TrieNode();
+                node = node->next[ch-'a'];
+            }
+            node->end = true;
+        }
+
+        return dfs(s,0);          
+    }
+
+    bool dfs(string&s, int cur)
+    {
+        if (memo[cur]==1) return false;
+
+        if (cur==s.size())
+            return true;
+
+        TrieNode* node = root;
+        for (int i=cur; i<s.size(); i++)
+        {           
+            if (node->next[s[i]-'a']!=NULL)
+            {
+                node = node->next[s[i]-'a'];
+                if (node->end==true && dfs(s, i+1))
+                    return true;
+            } else
+            {
+                break;
+            }
+        }
+
+        memo[cur] = 1;
+        return false;
+    }
+};