Sudoku Solver.cpp

// 37. Sudoku Solver

class Solution {
public:
    bool solve(vector<vector<char>>& board) {
        for (int i = 0; i < board.size(); i++) {
            for (int j = 0; j < board[0].size(); j++) {
                if (board[i][j] == '.') {
                    for (char c = '1'; c <= '9'; c++) {
                        if (isValid(board, i, j, c)) {
                            board[i][j] = c;
                            if (solve(board)) {
                                return true;
                            } else {
                                board[i][j] = '.';
                            }
                        }
                    }
                    return false; // Moved this line outside the inner loop
                }
            }
        }
        return true; // Moved this line outside the outer loop
    }

    bool isValid(vector<vector<char>>& board, int row, int col, char c) {
        for (int i = 0; i < 9; i++) {
            if (board[i][col] == c) {
                return false;
            }
            if (board[row][i] == c) {
                return false;
            }
            if (board[3 * (row / 3) + i / 3][3 * (col / 3) + i % 3] == c) {
                return false;
            }
        }
        return true;
    }

    void solveSudoku(vector<vector<char>>& board) {
        solve(board);
    }
};