Add CPP code for trie

Author: coderick14

trie.cpp

@@ -0,0 +1,56 @@
+#include <bits/stdc++.h>
+#define ll long long
+using namespace std;
+
+struct trie_node {
+    ll word_count;
+    ll prefix_count;
+    trie_node* edges[26];
+
+    trie_node() {
+        this->word_count = 0;
+        this->prefix_count = 0;
+        for(int i = 0; i < 26; i++) {
+            this->edges[i] = NULL;
+        }
+    }
+};
+
+void add_word(trie_node* &root, string &str, int index) {
+    if (index == str.length()) {
+        root->word_count += 1;
+        return;
+    }
+    root->prefix_count += 1;
+    int i = int(str[index] - 'a'); 
+    if (root->edges[i] == NULL) {
+        root->edges[i] = new trie_node();
+    }
+    add_word(root->edges[i], str, index+1);
+}
+
+ll count_prefix(trie_node* root, string &prefix, int index) {
+    if (index == prefix.length()) {
+        return root->prefix_count;
+    }
+    int i = int(prefix[index] - 'a');
+    if (root->edges[i] == NULL) {
+        return 0;
+    }
+    return count_prefix(root->edges[i], prefix, index+1);
+}
+
+int main() {
+    trie_node* root = new trie_node();
+    string s = "codechef";
+    add_word(root, s, 0);
+    s = "codeforces";
+    add_word(root, s, 0);
+    s = "youtube";
+    add_word(root, s, 0);
+    s = "google";
+    add_word(root, s, 0);
+    s = "code"; 
+    cout<<count_prefix(root, s, 0)<<endl;
+    return 0;
+}