184 lines
5.0 KiB
Java
184 lines
5.0 KiB
Java
package Others;
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// Java Program to implement Auto-Complete
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// Feature using Trie
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import java.util.*;
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import java.io.*;
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import java.lang.*;
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class Trieac {
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// Alphabet size (# of symbols)
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public static final int ALPHABET_SIZE = 26;
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// Trie node
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static class TrieNode
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{
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TrieNode children[] = new TrieNode[ALPHABET_SIZE];
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// isWordEnd is true if the node represents
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// end of a word
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boolean isWordEnd;
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};
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// Returns new trie node (initialized to NULLs)
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static TrieNode getNode() {
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TrieNode pNode = new TrieNode();
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pNode.isWordEnd = false;
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for(int i = 0; i < ALPHABET_SIZE; i++)
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pNode.children[i] = null;
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return pNode;
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}
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// If not present, inserts key into trie. If the
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// key is prefix of trie node, just marks leaf node
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static void insert(TrieNode root, final String key)
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{
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TrieNode pCrawl = root;
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for(int level = 0; level < key.length(); level++)
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{
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int index = (key.charAt(level) - 'a');
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if (pCrawl.children[index] == null)
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pCrawl.children[index] = getNode();
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pCrawl = pCrawl.children[index];
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}
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// mark last node as leaf
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pCrawl.isWordEnd = true;
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}
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// Returns true if key presents in trie, else false
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boolean search(TrieNode root, final String key)
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{
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int length = key.length();
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TrieNode pCrawl = root;
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for (int level = 0; level < length; level++)
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{
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int index = (key.charAt(level) - 'a');
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if (pCrawl.children[index] == null)
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pCrawl = pCrawl.children[index];
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}
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return (pCrawl != null && pCrawl.isWordEnd);
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}
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// Returns 0 if current node has a child
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// If all children are NULL, return 1.
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static boolean isLastNode(TrieNode root)
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{
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for (int i = 0; i < ALPHABET_SIZE; i++)
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if (root.children[i] != null)
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return false;
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return true;
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}
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// Recursive function to print auto-suggestions
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// for given node.
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static void suggestionsRec(TrieNode root, String currPrefix)
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{
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// found a string in Trie with the given prefix
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if (root.isWordEnd)
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{
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System.out.println(currPrefix);
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}
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// All children struct node pointers are NULL
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if (isLastNode(root))
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return;
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for (int i = 0; i < ALPHABET_SIZE; i++)
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{
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if (root.children[i] != null)
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{
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// append current character to currPrefix string
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currPrefix += (char)(97 + i);
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// recur over the rest
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suggestionsRec(root.children[i], currPrefix);
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}
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}
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}
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// Fucntion to print suggestions for
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// given query prefix.
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static int printAutoSuggestions(TrieNode root,
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final String query)
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{
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TrieNode pCrawl = root;
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// Check if prefix is present and find the
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// the node (of last level) with last character
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// of given string.
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int level;
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int n = query.length();
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for (level = 0; level < n; level++)
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{
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int index = (query.charAt(level) - 'a');
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// no string in the Trie has this prefix
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if (pCrawl.children[index] == null)
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return 0;
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pCrawl = pCrawl.children[index];
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}
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// If prefix is present as a word.
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boolean isWord = (pCrawl.isWordEnd == true);
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// If prefix is last node of tree (has no
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// children)
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boolean isLast = isLastNode(pCrawl);
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// If prefix is present as a word, but
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// there is no subtree below the last
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// matching node.
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if (isWord && isLast)
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{
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System.out.println(query);
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return -1;
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}
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// If there are are nodes below last
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// matching character.
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if (!isLast)
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{
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String prefix = query;
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suggestionsRec(pCrawl, prefix);
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return 1;
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}
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return 0;
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}
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// Driver code
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public static void main(String[] args)
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{
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TrieNode root = getNode();
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insert(root, "hello");
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insert(root, "dog");
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insert(root, "hell");
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insert(root, "cat");
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insert(root, "a");
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insert(root, "hel");
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insert(root, "help");
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insert(root, "helps");
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insert(root, "helping");
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int comp = printAutoSuggestions(root, "hel");
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if (comp == -1)
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System.out.println("No other strings found "+
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"with this prefix\n");
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else if (comp == 0)
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System.out.println("No string found with"+
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" this prefix\n");
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}
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}
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