Leetcode:sudoku Solver

Sudoku Solver, test instructions as follows:

Write a program to solve a Sudoku puzzle by filling the empty cells.

Empty cells is indicated by the character ‘.‘ .

Assume that there would be is only one unique solution.

A Sudoku Puzzle ...

... and its solution numbers marked in red.

That is to solve the ordinary Sudoku, began to think of a very naive simulation method, from only one possibility is the number can be determined to start filling, the result of course is not out of the way, because some places are more than one solution, because this problem in the classification of backtracking, and then think again.

Since there are a variety of solutions, it is possible to try the past, a solution can be output.

The process is as specific as can be understood:

Traverse the entire Sudoku table, once encountered a vacancy, fill in a 1, and then determine whether the 1 is in the row and column and the small nine Gongri is feasible, if feasible, go down, if not feasible, fill 2, repeat the above operation, have tried until 9.

First put the code:

public static void Solvesudoku (char[][] board) {Sudoku (board); } Static Boolean Sudoku (char[][] board) {for (int. i=0;i<9;i++) {for (int j=0;j<9;j++) {if (board[i][j] = = '. ') {for (int k=1;k<=9;k++) {Board[i][j] = (char) (' 0 ' +k), if (IsValid (board, I, J) && Sudoku (board)) {return true;} BOARD[I][J] = '. ';} return false;}}} return true;} Static Boolean IsValid (char[][] Board,int I,int j) {for (int a=0;a<9;a++) {if (board[i][j] = = Board[i][a] && a!=j Return false;if (board[i][j] = = Board[a][j] && a!=i) return false;} for (int a=3* (I/3), a<3* (i/3+1), a++) {for (int b=3* (J/3); b<3* (j/3+1); b++) {if (a!=i && b!=j && Board A [b] = = Board[i][j]) {return false;}}} return true;} public static void Main (string[] args) {char[][] a = {{'. ', '. ', ' 9 ', ' 7 ', ' 4 ', ' 8 ', '. ', '. ', '. ', ' {' 7 ', '. ', '. ', '. ', '. ', '. ' , '. ', '. ', '. '}, {'. ', ' 2 ', '. ', ' 1 ', '. ', ' 9 ', '. ', '. ', '. '}, {'. ', '. ', ' 7 ', '. ', '. ', '. ', ' 2 ', ' 4 ', '. '}, {'. ', ' 6 ', ' 4 ', ' . ', ' 1 ', '. ', ' 5 ', ' 9 ', '. '}, {'. ', ' 9 ', ' 8 ', '. ', '. ', '. ', ' 3 ', '. ', '. ', {'. ', '. ', '. ', ' 8 ', '. ', ' 3 ', '. ', ' 2 ', '. '}, {'. ', '. ', '. ', '. ', '. ', '. ', '. ', '. ', '. ', '. ', '. ', '. ', '. ' , ' 2 ', ' 7 ', ' 5 ', ' 9 ', '. ', '. '}; Solvesudoku (a); for (int. i=0;i<9;i++) {for (int j=0;j<9;j++) {System.out.print (a[i][j]+ "");} System.out.println ();}}

The secret of the code is only a tacit.

Leetcode:sudoku Solver