https://leetcode.com/problems/sudoku-solver/
Write a program to solve a Sudoku puzzle by filling the empty cells.
A sudoku solution must satisfy all of the following rules:
- Each of the digits
1-9
must occur exactly once in each row. - Each of the digits
1-9
must occur exactly once in each column. - Each of the the digits
1-9
must occur exactly once in each of the 93x3
sub-boxes of the grid.
Empty cells are indicated by the character '.'
.
A sudoku puzzle...
...and its solution numbers marked in red.
Note:
- The given board contain only digits
1-9
and the character'.'
. - You may assume that the given Sudoku puzzle will have a single unique solution.
- The given board size is always
9x9
.
代码:
class Solution { public: void solveSudoku(vector<vector<char> > &board) { if (board.empty() || board.size() != 9 || board[0].size() != 9) return; solveSudokuDFS(board, 0, 0); } bool solveSudokuDFS(vector<vector<char> > &board, int i, int j) { if (i == 9) return true; if (j >= 9) return solveSudokuDFS(board, i + 1, 0); if (board[i][j] == '.') { for (int k = 1; k <= 9; ++k) { board[i][j] = (char)(k + '0'); if (isValid(board, i , j)) { if (solveSudokuDFS(board, i, j + 1)) return true; } board[i][j] = '.'; } } else { return solveSudokuDFS(board, i, j + 1); } return false; } bool isValid(vector<vector<char> > &board, int i, int j) { for (int col = 0; col < 9; ++col) { if (col != j && board[i][j] == board[i][col]) return false; } for (int row = 0; row < 9; ++row) { if (row != i && board[i][j] == board[row][j]) return false; } for (int row = i / 3 * 3; row < i / 3 * 3 + 3; ++row) { for (int col = j / 3 * 3; col < j / 3 * 3 + 3; ++col) { if ((row != i || col != j) && board[i][j] == board[row][col]) return false; } } return true; } };
数独 9*9 暴力就好了