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Commit e34600d

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Improved trie code + leetcode longest word done
1 parent 8363578 commit e34600d

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2 files changed

+94
-28
lines changed

2 files changed

+94
-28
lines changed
Lines changed: 77 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,77 @@
1+
package com.leetcode.trie;
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import java.util.HashMap;
4+
import java.util.Stack;
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/**
7+
* Leetcode Problem: https://leetcode.com/problems/longest-word-in-dictionary/
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*
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* @author rampatra
10+
* @since 2019年04月10日
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*/
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public class LongestWord {
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private class TrieNode {
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char ch;
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HashMap<Character, TrieNode> children = new HashMap<>();
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String completeWord; // to mark a complete word in the tri data structure
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TrieNode(char ch) {
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this.ch = ch;
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}
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}
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private TrieNode root = new TrieNode('0');
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/**
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* Inserts {@code data} in trie.
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*
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* @param str
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*/
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public void insert(String str) {
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char c;
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TrieNode curr = root;
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for (int i = 0; i < str.length(); i++) {
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c = str.charAt(i);
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curr.children.putIfAbsent(c, new TrieNode(c));
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curr = curr.children.get(c);
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}
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curr.completeWord = str;
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}
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public String longestWord(String[] words) {
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for (int i = 0; i < words.length; i++) {
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insert(words[i]);
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}
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return longestWord();
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}
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private String longestWord() {
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String longestWord = "";
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TrieNode curr;
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Stack<TrieNode> stack = new Stack<>();
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stack.addAll(root.children.values());
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while (!stack.empty()) {
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curr = stack.pop();
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if (curr.completeWord != null) {
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if (curr.completeWord.length() > longestWord.length() ||
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(curr.completeWord.length() == longestWord.length() &&
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curr.completeWord.compareTo(longestWord) < 0)) {
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longestWord = curr.completeWord;
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}
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stack.addAll(curr.children.values());
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}
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}
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return longestWord;
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}
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public static void main(String[] args) {
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LongestWord longestWord = new LongestWord();
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System.out.println(longestWord.longestWord(new String[]{"w", "wo", "wor", "worl", "world"}));
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System.out.println(longestWord.longestWord(new String[]{"a", "banana", "app", "appl", "ap", "apply", "apple"}));
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}
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}

‎src/main/java/com/rampatra/base/Trie.java

Lines changed: 17 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -19,47 +19,37 @@
1919
* @author rampatra
2020
* @since 9/22/15
2121
*/
22-
public class Trie<E> {
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public class Trie {
2323

2424
private class TrieNode<T> {
25-
HashMap<T, TrieNode<T>> children;
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char ch;
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HashMap<T, TrieNode<T>> children = new HashMap<>();
2627
boolean isCompleteWord; // to mark a complete word in the tri data structure
2728

28-
TrieNode(HashMap<T, TrieNode<T>> children) {
29-
this.children = children;
29+
TrieNode(charch) {
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this.ch = ch;
3031
}
3132
}
3233

3334
private TrieNode<Character> root;
3435

3536
Trie() {
36-
root = new TrieNode<>(newHashMap<>());
37+
root = new TrieNode<>('0');
3738
}
3839

3940
/**
4041
* Inserts {@code data} in trie.
4142
*
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* @param data
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* @param str
4344
*/
44-
public void insert(E data) {
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46-
int i = 0;
47-
String str = data.toString();
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public void insert(String str) {
46+
char c;
4847
TrieNode<Character> curr = root;
4948

50-
while (i < str.length()) {
51-
if (curr.children.get(str.charAt(i)) != null) {
52-
curr = curr.children.get(str.charAt(i));
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i++;
54-
} else {
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break;
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}
57-
}
58-
59-
while (i < str.length()) {
60-
curr.children.put(str.charAt(i), new TrieNode<>(new HashMap<>()));
61-
curr = curr.children.get(str.charAt(i));
62-
i++;
49+
for (int i = 0; i < str.length(); i++) {
50+
c = str.charAt(i);
51+
curr.children.putIfAbsent(c, new TrieNode<>(c));
52+
curr = curr.children.get(c);
6353
}
6454

6555
curr.isCompleteWord = true;
@@ -68,12 +58,11 @@ public void insert(E data) {
6858
/**
6959
* Searches {@code data} in trie.
7060
*
71-
* @param data the value to search.
72-
* @return {@code true} if {@code data} is present, {@code false} otherwise.
61+
* @param str the value to search.
62+
* @return {@code true} if {@code str} is present, {@code false} otherwise.
7363
*/
74-
public boolean search(Edata) {
64+
public boolean search(Stringstr) {
7565

76-
String str = data.toString();
7766
TrieNode<Character> curr = root;
7867

7968
for (int i = 0; i < str.length(); i++) {
@@ -88,7 +77,7 @@ public boolean search(E data) {
8877

8978
// unit testing
9079
public static void main(String[] args) {
91-
Trie<String> trie = new Trie<>();
80+
Trie trie = new Trie();
9281
trie.insert("ram");
9382
trie.insert("r");
9483
trie.insert("rama");

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