Create main.cpp

Author: JawadSher

21 - Trie Data Structure Problems/03 - Longest Common Prefix/main.cpp

@@ -0,0 +1,89 @@
+class TrieNode{
+    public:
+        char data;
+        TrieNode* children[26];
+        int childCount;
+        bool isTerminal;
+
+        TrieNode(int data){
+            this -> data = data;
+            for(int i = 0; i < 26; i++) children[i] = NULL;
+            isTerminal = false;
+            childCount = 0;
+        }
+};
+
+class Trie{
+    public:
+        TrieNode* root;
+        Trie(char ch){ 
+            root = new TrieNode(ch);
+        }
+
+        void insertUtil(TrieNode* root, string& word, int index){
+            if(index == word.size()){
+                root -> isTerminal = true;
+                return;
+            }
+
+            int charIndex = word[index] - 'a';
+            if(root -> children[charIndex] == NULL){
+                root -> children[charIndex] = new TrieNode(word[index]);
+                root -> childCount++;
+            }
+
+            insertUtil(root -> children[charIndex], word, index+1);
+        }
+
+        void insertWord(string& word){
+            insertUtil(root, word, 0);
+        }
+
+        void lcp(string str, string& ans){
+            TrieNode* node = root;
+            for(int i = 0; i < str.length(); i++){
+                char ch = str[i];
+
+                if(node -> childCount == 1) {
+                    ans.push_back(ch);
+
+                    int index = ch - 'a';
+
+                    node = node -> children[index];
+                }else break;
+
+                if(node -> isTerminal) break;
+            }
+        }
+    
+    ~Trie() {
+        deleteTrie(root);
+    }
+    private:
+        void deleteTrie(TrieNode* node) {
+        if (!node) return;
+        for (int i = 0; i < 26; i++) {
+            deleteTrie(node->children[i]);
+        }
+        delete node;
+    }
+};
+class Solution {
+public:
+    string longestCommonPrefix(vector<string>& strs) {
+        if(strs.empty()) return "";
+
+        for(string& str : strs) if(str.empty()) return "";
+
+        Trie* t = new Trie('\0');
+
+        for(int i = 0; i < strs.size(); i++) t->insertWord(strs[i]);
+
+        string first = strs[0];
+        string ans = "";
+
+        t -> lcp(first, ans);
+
+        return ans;
+    }
+};