Trie

JAVA/DataStructures/Trie/CompleteString.java

@@ -0,0 +1,99 @@
+/**
+ * Question link: https://www.codingninjas.com/codestudio/problems/complete-string_2687860
+ */
+
+public class CompleteString {
+
+    public static void main(String[] args) {
+        String[] words = {"n", "ni", "nin", "ninj", "ninja", "ninga"};
+        Solution solution = new Solution();
+        String ans = solution.completeString(6, words);
+        System.out.println(ans);
+    }
+
+    static class Solution {
+
+        private static class TrieNode{
+            private TrieNode[] children;
+            int count;
+            boolean isEndOfWord;
+
+            TrieNode() {
+                children = new TrieNode[26];
+                count = 0;
+                isEndOfWord = false;
+            }
+
+            boolean containsChild(char c) {
+                return children[c - 97] == null;
+            }
+
+            TrieNode getChild(char c) {
+                return children[c - 97];
+            }
+
+            void addChild(char c) {
+                children[c - 97] = new TrieNode();
+            }
+
+            void setIsEndOfWord() {
+                isEndOfWord = true;
+            }
+
+            boolean getIsEndOfWord() {
+                return isEndOfWord;
+            }
+        }
+        public static String completeString(int n, String[] a) {
+            // Write your code here.
+            TrieNode root = new TrieNode();
+
+            for (String s: a)
+                createTrie(root, s, 0);
+
+            String ans = "";
+
+            for(String s: a)
+            {
+                if (isCompleteString(root, s, 0))
+                {
+                    if(s.length() > ans.length() || (ans.length() == s.length() && s.compareTo(ans) < 0))
+                        ans = s;
+                }
+            }
+            //String empty;
+            if (ans == "") return "None";
+            return ans;
+        }
+
+        private static void createTrie(TrieNode root, String s, int x) {
+            if (x == s.length()) {
+                root.setIsEndOfWord();
+                return;
+            }
+
+            char child = s.charAt(x);
+
+            if (root.containsChild(child)) {
+                root.addChild(child);
+            }
+
+            createTrie(root.getChild(child), s, x + 1);
+        }
+
+        private static boolean isCompleteString(TrieNode root, String s, int x) {
+            if (x == s.length())
+            {
+                return true;
+            }
+
+            char c = s.charAt(x);
+
+            TrieNode child = root.getChild(c);
+            if(!child.getIsEndOfWord())
+                return false;
+
+            return isCompleteString(child, s, x + 1);
+        }
+    }
+}

JAVA/DataStructures/Trie/LongestCommonPrefix.java

@@ -0,0 +1,64 @@
+/**
+ * GFG link: https://practice.geeksforgeeks.org/problems/longest-common-prefix-in-an-array5129/1
+ * This question can be solved in many ways, but this is the Trie or Prefix-Tree implementation for it.
+ * assuming the strings contain only lowercase words(the TrieNode data member 'next' data structure can be modified based on the requirement)
+ */
+
+public class LongestCommonPrefix {
+
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        String[] words = {"geeks", "geeksforgeeks", "geekds", "geekfs"};
+
+        System.out.println(solution.lcs(words));
+    }
+
+    static class Solution {
+
+        public String lcs(String[] words) {
+            TrieNode root = new TrieNode();
+
+            for (String word: words)
+                createTrie(word, 0, root);
+
+            int len = search(words[0], 0, root, words.length);
+            return len > 0 ? words[0].substring(0, len) : "-1";
+        }
+
+        //Trie class
+        private class TrieNode {
+            TrieNode[] next;
+            int count; //how many strings is the current substring a prefix
+
+            TrieNode() {
+                next = new TrieNode[26];
+                count = 0;
+            }
+        }
+
+        private void createTrie(String s, int in, TrieNode parent) {
+            if(in == s.length()) {
+                return;
+            }
+
+            if(parent.next[s.charAt(in) - 'a'] == null)
+                parent.next[s.charAt(in) - 'a'] = new TrieNode();
+
+            parent.next[s.charAt(in) - 'a'].count++;
+
+            createTrie(s, in + 1, parent.next[s.charAt(in) - 'a']);
+        }
+
+        private int search(String s, int in, TrieNode parent, int totalWords) {
+            if(in == s.length()) {
+                return s.length();
+            }
+
+            if(parent.next[s.charAt(in) - 'a'].count != totalWords) {
+                return in;
+            }
+
+            return search(s, in + 1, parent.next[s.charAt(in) - 'a'], totalWords);
+        }
+    }
+}

JAVA/DataStructures/Trie/NumberOfDistinctSubstring.java

@@ -0,0 +1,67 @@
+/**
+ * Question link: https://www.codingninjas.com/codestudio/problems/number-of-distinct-substring_1465938
+ */
+
+import java.util.*;
+
+public class NumberOfDistinctSubstring {
+
+    public static void main(String[] args) {
+        String word = "abccbc";
+        Solution solution = new Solution();
+        int ans = solution.distinctSubstring(word);
+        System.out.println(ans);
+    }
+
+    static class Solution {
+
+        private static class TrieNode {
+            Map<Character, TrieNode> next;
+
+            TrieNode() {
+                next = new HashMap<>();
+            }
+
+            boolean contains(char c) {
+                return next.containsKey(c);
+            }
+            void add(char c) {
+                next.put(c, new TrieNode());
+                return;
+            }
+
+            TrieNode get(char c) {
+                return next.get(c);
+            }
+        }
+        public static int distinctSubstring(String st)
+        {
+            //your code here
+            TrieNode root = new TrieNode();
+            int length = 0;
+            for(int i = 0; i < st.length(); i++)
+            {
+                length+=createTrie(st, i, root);
+            }
+
+            return length;
+        }
+
+        private static int createTrie(String s, int x, TrieNode root)
+        {
+            if(x == s.length())
+                return 0;
+
+            char c = s.charAt(x++);
+
+            int count = 0;
+            if(!root.contains(c))
+            {
+                count = 1;
+                root.add(c);
+            }
+            TrieNode next = root.get(c);
+            return count + createTrie(s, x, next);
+        }
+    }
+}

JAVA/DataStructures/Trie/ShortestUniquePrefix.java

@@ -0,0 +1,90 @@
+/**
+ * Question link: https://practice.geeksforgeeks.org/problems/shortest-unique-prefix-for-every-word/1
+ */
+
+import java.util.*;
+
+public class ShortestUniquePrefix {
+
+    public static void main(String[] args) {
+        String[] words = {"zebra", "dog", "duck", "dove"};
+
+        Solution solution = new Solution();
+        String[] prefixes = solution.findPrefixes(words, 4);
+
+        for(String s: prefixes)
+            System.out.println(s);
+    }
+
+     static class Solution {
+        static class TrieNode {
+            char val;
+            int count;
+            Map<Character, TrieNode> next;
+
+            TrieNode() {
+                count = 0;
+                next = new HashMap<Character, TrieNode>();
+            }
+
+            TrieNode(char c) {
+                count = 1;
+                val = c;
+                next = new HashMap<Character, TrieNode>();
+            }
+
+            void insert(char c) {
+                next.put(c, new TrieNode(c));
+            }
+
+            void incCount() {
+                count++;
+            }
+        }
+
+        static String[] findPrefixes(String[] arr, int N) {
+            // code here
+            TrieNode root = new TrieNode();
+
+            for(String s: arr) {
+                createTrie(root, s, 0);
+            }
+
+            String[] prefixes = new String[N];
+            int i = 0;
+            for(String s: arr) {
+                prefixes[i++] = getPrefix(root, s, 0, new StringBuilder(""));
+            }
+
+            return prefixes;
+        }
+
+        private static void createTrie(TrieNode root, String s, int x) {
+            if(x == s.length())
+                return;
+
+            char c = s.charAt(x);
+
+            if(!root.next.containsKey(c)) {
+                root.insert(c);
+            }
+            else {
+                root.next.get(c).incCount();
+            }
+
+            createTrie(root.next.get(c), s, x+1);
+        }
+
+        private static String getPrefix(TrieNode root, String s, int x, StringBuilder st) {
+            if(root.count == 1)
+                return st.toString();
+
+            char c = s.charAt(x);
+
+            st.append(c);
+
+            return getPrefix(root.next.get(c), s, x + 1, st);
+
+        }
+    }
+}