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BamaCharanChhandogiBamaCharanChhandogi
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Merge branch 'master' into improve-power-sum-algorithm
2 parents 4668a37 + d437d58 commit dc0244e

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‎DIRECTORY.md‎

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* [AllPathsFromSourceToTarget](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/AllPathsFromSourceToTarget.java)
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* [ArrayCombination](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/ArrayCombination.java)
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* [Combination](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/Combination.java)
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* [CrosswordSolver](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/CrosswordSolver.java)
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* [FloodFill](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/FloodFill.java)
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* [KnightsTour](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/KnightsTour.java)
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* [MazeRecursion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/MazeRecursion.java)
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* [Permutation](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/Permutation.java)
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* [PowerSum](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/PowerSum.java)
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* [SubsequenceFinder](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/SubsequenceFinder.java)
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* [WordPatternMatcher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/WordPatternMatcher.java)
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* [WordSearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/WordSearch.java)
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* bitmanipulation
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* [BitSwap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/BitSwap.java)
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* [PrefixToInfix](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/stacks/PrefixToInfix.java)
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* [SortStack](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/stacks/SortStack.java)
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* [StackPostfixNotation](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/stacks/StackPostfixNotation.java)
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* [StackUsingTwoQueues](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/stacks/StackUsingTwoQueues.java)
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* strings
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* [AhoCorasick](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/AhoCorasick.java)
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* [Alphabetical](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/Alphabetical.java)
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* [AllPathsFromSourceToTargetTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/AllPathsFromSourceToTargetTest.java)
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* [ArrayCombinationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/ArrayCombinationTest.java)
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* [CombinationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/CombinationTest.java)
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* [CrosswordSolverTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/CrosswordSolverTest.java)
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* [FloodFillTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/FloodFillTest.java)
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* [KnightsTourTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/KnightsTourTest.java)
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* [MazeRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/MazeRecursionTest.java)
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* [PermutationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/PermutationTest.java)
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* [PowerSumTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/PowerSumTest.java)
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* [SubsequenceFinderTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/SubsequenceFinderTest.java)
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* [WordPatternMatcherTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/WordPatternMatcherTest.java)
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* [WordSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/WordSearchTest.java)
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* bitmanipulation
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* [BitSwapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/BitSwapTest.java)
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* [BoruvkaAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/BoruvkaAlgorithmTest.java)
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* [DijkstraAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/DijkstraAlgorithmTest.java)
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* [EdmondsBlossomAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/EdmondsBlossomAlgorithmTest.java)
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* [FloydWarshallTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/FloydWarshallTest.java)
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* [FordFulkersonTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/FordFulkersonTest.java)
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* [HamiltonianCycleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/HamiltonianCycleTest.java)
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* [KosarajuTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/KosarajuTest.java)
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* [PrefixToInfixTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/PrefixToInfixTest.java)
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* [SortStackTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/SortStackTest.java)
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* [StackPostfixNotationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/StackPostfixNotationTest.java)
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* [StackUsingTwoQueuesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/StackUsingTwoQueuesTest.java)
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* strings
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* [AhoCorasickTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/AhoCorasickTest.java)
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* [AlphabeticalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java)

‎src/main/java/com/thealgorithms/backtracking/CrosswordSolver.java‎

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package com.thealgorithms.backtracking;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* A class to solve a crossword puzzle using backtracking.
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* Example:
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* Input:
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* puzzle = {
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* {' ', ' ', ' '},
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* {' ', ' ', ' '},
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* {' ', ' ', ' '}
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* }
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* words = List.of("cat", "dog")
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*
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* Output:
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* {
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* {'c', 'a', 't'},
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* {' ', ' ', ' '},
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* {'d', 'o', 'g'}
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* }
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*/
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public final class CrosswordSolver {
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private CrosswordSolver() {
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}
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/**
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* Checks if a word can be placed at the specified position in the crossword.
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*
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* @param puzzle The crossword puzzle represented as a 2D char array.
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* @param word The word to be placed.
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* @param row The row index where the word might be placed.
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* @param col The column index where the word might be placed.
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* @param vertical If true, the word is placed vertically; otherwise, horizontally.
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* @return true if the word can be placed, false otherwise.
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*/
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public static boolean isValid(char[][] puzzle, String word, int row, int col, boolean vertical) {
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for (int i = 0; i < word.length(); i++) {
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if (vertical) {
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if (row + i >= puzzle.length || puzzle[row + i][col] != ' ') {
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return false;
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}
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} else {
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if (col + i >= puzzle[0].length || puzzle[row][col + i] != ' ') {
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return false;
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}
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}
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}
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return true;
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}
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/**
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* Places a word at the specified position in the crossword.
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*
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* @param puzzle The crossword puzzle represented as a 2D char array.
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* @param word The word to be placed.
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* @param row The row index where the word will be placed.
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* @param col The column index where the word will be placed.
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* @param vertical If true, the word is placed vertically; otherwise, horizontally.
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*/
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public static void placeWord(char[][] puzzle, String word, int row, int col, boolean vertical) {
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for (int i = 0; i < word.length(); i++) {
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if (vertical) {
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puzzle[row + i][col] = word.charAt(i);
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} else {
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puzzle[row][col + i] = word.charAt(i);
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}
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}
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}
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/**
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* Removes a word from the specified position in the crossword.
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*
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* @param puzzle The crossword puzzle represented as a 2D char array.
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* @param word The word to be removed.
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* @param row The row index where the word is placed.
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* @param col The column index where the word is placed.
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* @param vertical If true, the word was placed vertically; otherwise, horizontally.
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*/
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public static void removeWord(char[][] puzzle, String word, int row, int col, boolean vertical) {
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for (int i = 0; i < word.length(); i++) {
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if (vertical) {
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puzzle[row + i][col] = ' ';
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} else {
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puzzle[row][col + i] = ' ';
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}
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}
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}
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/**
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* Solves the crossword puzzle using backtracking.
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*
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* @param puzzle The crossword puzzle represented as a 2D char array.
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* @param words The list of words to be placed.
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* @return true if the crossword is solved, false otherwise.
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*/
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public static boolean solveCrossword(char[][] puzzle, List<String> words) {
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// Create a mutable copy of the words list
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List<String> remainingWords = new ArrayList<>(words);
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for (int row = 0; row < puzzle.length; row++) {
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for (int col = 0; col < puzzle[0].length; col++) {
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if (puzzle[row][col] == ' ') {
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for (String word : new ArrayList<>(remainingWords)) {
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for (boolean vertical : new boolean[] {true, false}) {
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if (isValid(puzzle, word, row, col, vertical)) {
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placeWord(puzzle, word, row, col, vertical);
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remainingWords.remove(word);
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if (solveCrossword(puzzle, remainingWords)) {
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return true;
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}
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remainingWords.add(word);
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removeWord(puzzle, word, row, col, vertical);
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}
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}
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}
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return false;
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}
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}
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}
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return true;
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}
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}

‎src/main/java/com/thealgorithms/backtracking/WordPatternMatcher.java‎

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package com.thealgorithms.backtracking;
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import java.util.HashMap;
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import java.util.Map;
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/**
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* Class to determine if a pattern matches a string using backtracking.
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*
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* Example:
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* Pattern: "abab"
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* Input String: "JavaPythonJavaPython"
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* Output: true
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*
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* Pattern: "aaaa"
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* Input String: "JavaJavaJavaJava"
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* Output: true
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*
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* Pattern: "aabb"
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* Input String: "JavaPythonPythonJava"
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* Output: false
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*/
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public final class WordPatternMatcher {
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private WordPatternMatcher() {
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}
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/**
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* Determines if the given pattern matches the input string using backtracking.
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*
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* @param pattern The pattern to match.
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* @param inputString The string to match against the pattern.
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* @return True if the pattern matches the string, False otherwise.
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*/
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public static boolean matchWordPattern(String pattern, String inputString) {
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Map<Character, String> patternMap = new HashMap<>();
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Map<String, Character> strMap = new HashMap<>();
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return backtrack(pattern, inputString, 0, 0, patternMap, strMap);
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}
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/**
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* Backtracking helper function to check if the pattern matches the string.
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*
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* @param pattern The pattern string.
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* @param inputString The string to match against the pattern.
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* @param patternIndex Current index in the pattern.
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* @param strIndex Current index in the input string.
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* @param patternMap Map to store pattern characters to string mappings.
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* @param strMap Map to store string to pattern character mappings.
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* @return True if the pattern matches, False otherwise.
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*/
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private static boolean backtrack(String pattern, String inputString, int patternIndex, int strIndex, Map<Character, String> patternMap, Map<String, Character> strMap) {
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if (patternIndex == pattern.length() && strIndex == inputString.length()) {
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return true;
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}
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if (patternIndex == pattern.length() || strIndex == inputString.length()) {
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return false;
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}
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char currentChar = pattern.charAt(patternIndex);
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if (patternMap.containsKey(currentChar)) {
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String mappedStr = patternMap.get(currentChar);
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if (inputString.startsWith(mappedStr, strIndex)) {
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return backtrack(pattern, inputString, patternIndex + 1, strIndex + mappedStr.length(), patternMap, strMap);
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} else {
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return false;
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}
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}
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for (int end = strIndex + 1; end <= inputString.length(); end++) {
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String substring = inputString.substring(strIndex, end);
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if (strMap.containsKey(substring)) {
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continue;
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}
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patternMap.put(currentChar, substring);
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strMap.put(substring, currentChar);
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if (backtrack(pattern, inputString, patternIndex + 1, end, patternMap, strMap)) {
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return true;
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}
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patternMap.remove(currentChar);
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strMap.remove(substring);
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}
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return false;
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}
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}

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