implementing Recursive Backtracking in Sudoku Solver - Stack Overflow scenarios in Java
After trying multiple solutions online, I still can't figure this out. I'm reviewing some code and I'm currently implementing a Sudoku solver using the recursive backtracking algorithm in Java, but I'm running into a `StackOverflowError` when attempting to solve certain puzzles. The goal is to fill a 9x9 grid such that each row, column, and 3x3 box contains the digits 1 through 9 exactly once. I've defined a `solve` method that recursively attempts to fill in the grid. Here's a simplified version of my code: ```java public class SudokuSolver { private static final int SIZE = 9; private int[][] board; public SudokuSolver(int[][] board) { this.board = board; } public boolean solve() { for (int row = 0; row < SIZE; row++) { for (int col = 0; col < SIZE; col++) { if (board[row][col] == 0) { // 0 means empty cell for (int num = 1; num <= SIZE; num++) { if (isValid(row, col, num)) { board[row][col] = num; if (solve()) { return true; } board[row][col] = 0; // backtrack } } return false; // if no number is valid } } } return true; // solved } private boolean isValid(int row, int col, int num) { // Check row and column for (int i = 0; i < SIZE; i++) { if (board[row][i] == num || board[i][col] == num) { return false; } } // Check 3x3 box int boxRowStart = row - row % 3; int boxColStart = col - col % 3; for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { if (board[i + boxRowStart][j + boxColStart] == num) { return false; } } } return true; } } ``` I believe the main scenario might be with the base case logic or the way the backtracking is implemented, but I need to pinpoint the question. When attempting to solve specific puzzles, the recursion depth increases significantly, leading to a `StackOverflowError`. I've also tried optimizing the algorithm by breaking out of loops early when possible, but the behavior continues. Any insights or suggestions on what might be causing this scenario would be greatly appreciated! Thanks for taking the time to read this! What am I doing wrong? I've been using Java for about a year now. I'm open to any suggestions. What are your experiences with this?