Issue #291 Implement Trie data structure

Author: bhavik-m

Data Structures/Trie/Implement_trie.cpp

@@ -0,0 +1,89 @@
+// C++ implementation of search and insert
+// operations on Trie
+#include <bits/stdc++.h>
+using namespace std;
+
+const int ALPHABET_SIZE = 26;
+
+// trie node
+struct TrieNode
+{
+    struct TrieNode *children[ALPHABET_SIZE];
+
+    // isEndOfWord is true if the node represents
+    // end of a word
+    bool isEndOfWord;
+};
+
+// Returns new trie node (initialized to NULLs)
+struct TrieNode *getNode(void)
+{
+    struct TrieNode *pNode = new TrieNode;
+
+    pNode->isEndOfWord = false;
+
+    for (int i = 0; i < ALPHABET_SIZE; i++)
+        pNode->children[i] = NULL;
+
+    return pNode;
+}
+
+// If not present, inserts key into trie
+// If the key is prefix of trie node, just
+// marks leaf node
+void insert(struct TrieNode *root, string key)
+{
+    struct TrieNode *pCrawl = root;
+
+    for (int i = 0; i < key.length(); i++)
+    {
+        int index = key[i] - 'a';
+        if (!pCrawl->children[index])
+            pCrawl->children[index] = getNode();
+
+        pCrawl = pCrawl->children[index];
+    }
+
+    // mark last node as leaf
+    pCrawl->isEndOfWord = true;
+}
+
+// Returns true if key presents in trie, else
+// false
+bool search(struct TrieNode *root, string key)
+{
+    struct TrieNode *pCrawl = root;
+
+    for (int i = 0; i < key.length(); i++)
+    {
+        int index = key[i] - 'a';
+        if (!pCrawl->children[index])
+            return false;
+
+        pCrawl = pCrawl->children[index];
+    }
+
+    return (pCrawl->isEndOfWord);
+}
+
+// Driver
+int main()
+{
+    // Input keys (use only 'a' through 'z'
+    // and lower case)
+    string keys[] = {"the", "a", "there",
+                     "answer", "any", "by",
+                     "bye", "their"};
+    int n = sizeof(keys) / sizeof(keys[0]);
+
+    struct TrieNode *root = getNode();
+
+    // Construct trie
+    for (int i = 0; i < n; i++)
+        insert(root, keys[i]);
+
+    // Search for different keys
+    search(root, "the") ? cout << "Yes\n" : cout << "No\n";
+    search(root, "these") ? cout << "Yes\n" : cout << "No\n";
+    return 0;
+}