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WordBoggle.java
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154 lines (131 loc) · 4.49 KB
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package com.thealgorithms.misc;
import java.util.*;
public class WordBoggle {
/**
* O(nm * 8^s + ws) time where n = width of boggle board, m = height of
* boggle board, s = length of longest word in string array, w = length of
* string array, 8 is due to 8 explorable neighbours O(nm + ws) space.
*/
public static List<String> boggleBoard(char[][] board, String[] words) {
Trie trie = new Trie();
for (String word : words) {
trie.add(word);
}
Set<String> finalWords = new HashSet<>();
boolean[][] visited = new boolean[board.length][board.length];
for (int i = 0; i < board.length; i++) {
for (int j = 0; j < board[i].length; j++) {
explore(i, j, board, trie.root, visited, finalWords);
}
}
return new ArrayList<>(finalWords);
}
public static void main(String[] args) {
// Testcase
List<String> ans
= new ArrayList<>(
Arrays.asList("a", "boggle", "this", "NOTRE_PEATED", "is", "simple", "board"));
assert (boggleBoard(
new char[][]{
{'t', 'h', 'i', 's', 'i', 's', 'a'},
{'s', 'i', 'm', 'p', 'l', 'e', 'x'},
{'b', 'x', 'x', 'x', 'x', 'e', 'b'},
{'x', 'o', 'g', 'g', 'l', 'x', 'o'},
{'x', 'x', 'x', 'D', 'T', 'r', 'a'},
{'R', 'E', 'P', 'E', 'A', 'd', 'x'},
{'x', 'x', 'x', 'x', 'x', 'x', 'x'},
{'N', 'O', 'T', 'R', 'E', '_', 'P'},
{'x', 'x', 'D', 'E', 'T', 'A', 'E'},},
new String[]{
"this",
"is",
"not",
"a",
"simple",
"test",
"boggle",
"board",
"REPEATED",
"NOTRE_PEATED",})
.equals(ans));
}
public static void explore(
int i,
int j,
char[][] board,
TrieNode trieNode,
boolean[][] visited,
Set<String> finalWords) {
if (visited[i][j]) {
return;
}
char letter = board[i][j];
if (!trieNode.children.containsKey(letter)) {
return;
}
visited[i][j] = true;
trieNode = trieNode.children.get(letter);
if (trieNode.children.containsKey('*')) {
finalWords.add(trieNode.word);
}
List<Integer[]> neighbors = getNeighbors(i, j, board);
for (Integer[] neighbor : neighbors) {
explore(neighbor[0], neighbor[1], board, trieNode, visited, finalWords);
}
visited[i][j] = false;
}
public static List<Integer[]> getNeighbors(int i, int j, char[][] board) {
List<Integer[]> neighbors = new ArrayList<>();
if (i > 0 && j > 0) {
neighbors.add(new Integer[]{i - 1, j - 1});
}
if (i > 0 && j < board[0].length - 1) {
neighbors.add(new Integer[]{i - 1, j + 1});
}
if (i < board.length - 1 && j < board[0].length - 1) {
neighbors.add(new Integer[]{i + 1, j + 1});
}
if (i < board.length - 1 && j > 0) {
neighbors.add(new Integer[]{i + 1, j - 1});
}
if (i > 0) {
neighbors.add(new Integer[]{i - 1, j});
}
if (i < board.length - 1) {
neighbors.add(new Integer[]{i + 1, j});
}
if (j > 0) {
neighbors.add(new Integer[]{i, j - 1});
}
if (j < board[0].length - 1) {
neighbors.add(new Integer[]{i, j + 1});
}
return neighbors;
}
}
// Trie used to optimize string search
class TrieNode {
Map<Character, TrieNode> children = new HashMap<>();
String word = "";
}
class Trie {
TrieNode root;
char endSymbol;
public Trie() {
this.root = new TrieNode();
this.endSymbol = '*';
}
public void add(String str) {
TrieNode node = this.root;
for (int i = 0; i < str.length(); i++) {
char letter = str.charAt(i);
if (!node.children.containsKey(letter)) {
TrieNode newNode = new TrieNode();
node.children.put(letter, newNode);
}
node = node.children.get(letter);
}
node.children.put(this.endSymbol, null);
node.word = str;
}
}