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feat: add Sudoku Solver using Backtracking (#7073)

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* feat: add Sudoku Solver using Backtracking (issue #6929)

* refactor: remove old Sudoku class from puzzlesandgames package

* Remove old Sudoku implementation and its test class
This commit is contained in:
GOPISETTI NAVADEEP
2025-11-17 14:24:20 +05:30
committed by GitHub
parent cff5d3662e
commit 9f2b675f3e
4 changed files with 210 additions and 207 deletions
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53
src/test/java/com/thealgorithms/backtracking/SudokuSolverTest.java Normal file
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package com.thealgorithms.backtracking;
import static org.junit.jupiter.api.Assertions.assertArrayEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertTrue;
import org.junit.jupiter.api.Test;
class SudokuSolverTest {
@Test
void testSolveSudokuEasyPuzzle() {
int[][] board = {{5, 3, 0, 0, 7, 0, 0, 0, 0}, {6, 0, 0, 1, 9, 5, 0, 0, 0}, {0, 9, 8, 0, 0, 0, 0, 6, 0}, {8, 0, 0, 0, 6, 0, 0, 0, 3}, {4, 0, 0, 8, 0, 3, 0, 0, 1}, {7, 0, 0, 0, 2, 0, 0, 0, 6}, {0, 6, 0, 0, 0, 0, 2, 8, 0}, {0, 0, 0, 4, 1, 9, 0, 0, 5}, {0, 0, 0, 0, 8, 0, 0, 7, 9}};
assertTrue(SudokuSolver.solveSudoku(board));
int[][] expected = {{5, 3, 4, 6, 7, 8, 9, 1, 2}, {6, 7, 2, 1, 9, 5, 3, 4, 8}, {1, 9, 8, 3, 4, 2, 5, 6, 7}, {8, 5, 9, 7, 6, 1, 4, 2, 3}, {4, 2, 6, 8, 5, 3, 7, 9, 1}, {7, 1, 3, 9, 2, 4, 8, 5, 6}, {9, 6, 1, 5, 3, 7, 2, 8, 4}, {2, 8, 7, 4, 1, 9, 6, 3, 5}, {3, 4, 5, 2, 8, 6, 1, 7, 9}};
assertArrayEquals(expected, board);
}
@Test
void testSolveSudokuHardPuzzle() {
int[][] board = {{0, 0, 0, 0, 0, 0, 6, 8, 0}, {0, 0, 0, 0, 7, 3, 0, 0, 9}, {3, 0, 9, 0, 0, 0, 0, 4, 5}, {4, 9, 0, 0, 0, 0, 0, 0, 0}, {8, 0, 3, 0, 5, 0, 9, 0, 2}, {0, 0, 0, 0, 0, 0, 0, 3, 6}, {9, 6, 0, 0, 0, 0, 3, 0, 8}, {7, 0, 0, 6, 8, 0, 0, 0, 0}, {0, 2, 8, 0, 0, 0, 0, 0, 0}};
assertTrue(SudokuSolver.solveSudoku(board));
}
@Test
void testSolveSudokuAlreadySolved() {
int[][] board = {{5, 3, 4, 6, 7, 8, 9, 1, 2}, {6, 7, 2, 1, 9, 5, 3, 4, 8}, {1, 9, 8, 3, 4, 2, 5, 6, 7}, {8, 5, 9, 7, 6, 1, 4, 2, 3}, {4, 2, 6, 8, 5, 3, 7, 9, 1}, {7, 1, 3, 9, 2, 4, 8, 5, 6}, {9, 6, 1, 5, 3, 7, 2, 8, 4}, {2, 8, 7, 4, 1, 9, 6, 3, 5}, {3, 4, 5, 2, 8, 6, 1, 7, 9}};
assertTrue(SudokuSolver.solveSudoku(board));
}
@Test
void testSolveSudokuInvalidSize() {
int[][] board = {{1, 2, 3}, {4, 5, 6}};
assertFalse(SudokuSolver.solveSudoku(board));
}
@Test
void testSolveSudokuNullBoard() {
assertFalse(SudokuSolver.solveSudoku(null));
}
@Test
void testSolveSudokuEmptyBoard() {
int[][] board = {{0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0}};
assertTrue(SudokuSolver.solveSudoku(board));
}
}

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src/test/java/com/thealgorithms/puzzlesandgames/SudokuTest.java
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package com.thealgorithms.puzzlesandgames;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;
import org.junit.jupiter.api.Test;
public class SudokuTest {
@Test
void testIsSafe2() {
int[][] board = {{3, 0, 6, 5, 0, 8, 4, 0, 0}, {5, 2, 0, 0, 0, 0, 0, 0, 0}, {0, 8, 7, 0, 0, 0, 0, 3, 1}, {0, 0, 3, 0, 1, 0, 0, 8, 0}, {9, 0, 0, 8, 6, 3, 0, 0, 5}, {0, 5, 0, 0, 9, 0, 6, 0, 0}, {1, 3, 0, 0, 0, 0, 2, 5, 0}, {0, 0, 0, 0, 0, 0, 0, 7, 4}, {0, 0, 5, 2, 0, 6, 3, 0, 0}};
assertFalse(Sudoku.isSafe(board, 0, 1, 3));
assertTrue(Sudoku.isSafe(board, 1, 2, 1));
assertThrows(ArrayIndexOutOfBoundsException.class, () -> { Sudoku.isSafe(board, 10, 10, 5); });
assertThrows(ArrayIndexOutOfBoundsException.class, () -> { Sudoku.isSafe(board, -1, 0, 5); });
}
@Test
void testSolveSudoku() {
int[][] board = {{3, 0, 6, 5, 0, 8, 4, 0, 0}, {5, 2, 0, 0, 0, 0, 0, 0, 0}, {0, 8, 7, 0, 0, 0, 0, 3, 1}, {0, 0, 3, 0, 1, 0, 0, 8, 0}, {9, 0, 0, 8, 6, 3, 0, 0, 5}, {0, 5, 0, 0, 9, 0, 6, 0, 0}, {1, 3, 0, 0, 0, 0, 2, 5, 0}, {0, 0, 0, 0, 0, 0, 0, 7, 4}, {0, 0, 5, 2, 0, 6, 3, 0, 0}};
assertTrue(Sudoku.solveSudoku(board, board.length));
assertEquals(1, board[0][1]);
assertThrows(ArrayIndexOutOfBoundsException.class, () -> { Sudoku.solveSudoku(board, 10); });
assertTrue(Sudoku.solveSudoku(board, -1));
}
@Test
void testUnsolvableSudoku() {
int[][] unsolvableBoard = {{5, 1, 6, 8, 4, 9, 7, 3, 2}, {3, 0, 7, 6, 0, 5, 0, 0, 0}, {8, 0, 9, 7, 0, 0, 0, 6, 5}, {1, 3, 5, 0, 6, 0, 9, 0, 7}, {4, 7, 2, 5, 9, 1, 0, 0, 6}, {9, 6, 8, 3, 7, 0, 0, 5, 0}, {2, 5, 3, 1, 8, 6, 0, 7, 4}, {6, 8, 4, 2, 5, 7, 3, 9, 0}, {7, 9, 1, 4, 3, 0, 5, 0, 0}};
assertFalse(Sudoku.solveSudoku(unsolvableBoard, unsolvableBoard.length));
}
}