Sudoku Solver
Write a program to solve a Sudoku puzzle by filling the empty cells.
Empty cells are indicated by the character '.'.
You may assume that there will be only one unique solution.
A sudoku puzzle...
...and its solution numbers marked in red.
思路：
搜索，类似八皇后
代码：
1 bool search(vector<vector<char> > &board, vector<vector<bool> > &rows, vector<vector<bool> > &cols, vector<vector<bool> > &blocks, int x, int y){ 2 if(x == 9 && y == 0) 3 return true; 4 int nx, ny; 5 ny = y+1; 6 nx = x; 7 if(ny == 9){ 8 ny = 0; 9 nx++; 10 } 11 if(board[x][y] != '.'){ 12 return search(board, rows, cols, blocks, nx, ny); 13 } 14 else{ 15 for(int i = 0; i < 9; i++){ 16 if(!rows[x][i] && !cols[y][i] && !blocks[x/3*3+y/3][i]){ 17 rows[x][i] = true; 18 cols[y][i] = true; 19 blocks[x/3*3+y/3][i] = true; 20 board[x][y] = i+1+'0'; 21 if(search(board, rows, cols, blocks, nx, ny)) 22 return true; 23 board[x][y] = '.'; 24 rows[x][i] = false; 25 cols[y][i] = false; 26 blocks[x/3*3+y/3][i] = false; 27 } 28 } 29 return false; 30 } 31 } 32 void solveSudoku(vector<vector<char> > &board) { 33 // IMPORTANT: Please reset any member data you declared, as 34 // the same Solution instance will be reused for each test case. 35 vector<vector<bool> > rows(9, vector<bool>(9, false)); 36 vector<vector<bool> > cols(9, vector<bool>(9, false)); 37 vector<vector<bool> > blocks(9, vector<bool>(9, false)); 38 for(int i = 0; i < 9; i++){ 39 for(int j = 0; j < 9; j++){ 40 if(board[i][j] != '.'){ 41 int num = board[i][j]-'0'; 42 rows[i][num-1] = true; 43 cols[j][num-1] = true; 44 blocks[i/3*3+j/3][num-1] = true; 45 } 46 } 47 } 48 search(board, rows, cols, blocks, 0, 0); 49 }
