week7-work1

70works/week7/work/day46_208_implement-trie-prefix-tree.cpp

+class Trie {
+    struct TrieNode {
+        map<char, TrieNode*> child_table;
+        int end;
+        TrieNode():end(0) {};
+    };
+public:
+    /** Initialize your data structure here. */
+    Trie() {
+        root = new TrieNode();
+    }
+    
+    /** Inserts a word into the trie. */
+    void insert(string word) {
+        TrieNode* cur = root;
+        for(int i =0; i < word.size(); i++) {
+            if(cur->child_table.count(word[i]) == 0) {
+                cur->child_table[word[i]] = new TrieNode();
+            }
+            cur =cur->child_table[word[i]];
+        }
+        cur->end=1;
+
+    }
+    
+    /** Returns if the word is in the trie. */
+    bool search(string word) {
+        return find(word, 1);
+
+    }
+    
+    /** Returns if there is any word in the trie that starts with the given prefix. */
+    bool startsWith(string prefix) {
+        return find(prefix, 0);
+    }
+    private:
+    TrieNode *root;
+    bool find(string prefix, int exact_match) {
+        TrieNode *cur = root;
+        for(int i =0; i<prefix.size(); i++) {
+            if(cur->child_table.count(prefix[i]) == 0) {
+                return false;
+            }
+            cur = cur->child_table[prefix[i]];
+        }
+
+        if(exact_match) {
+            return cur->end? true: false;
+        }
+        return true;
+    }
+};
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * Trie* obj = new Trie();
+ * obj->insert(word);
+ * bool param_2 = obj->search(word);
+ * bool param_3 = obj->startsWith(prefix);
+ */
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