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 digits
1-9
must occur exactly once in each of the 93x3
sub-boxes of the grid.
The '.'
character indicates empty cells.
Example 1:
Input: board = [["5","3",".",".","7",".",".",".","."],["6",".",".","1","9","5",".",".","."],[".","9","8",".",".",".",".","6","."],["8",".",".",".","6",".",".",".","3"],["4",".",".","8",".","3",".",".","1"],["7",".",".",".","2",".",".",".","6"],[".","6",".",".",".",".","2","8","."],[".",".",".","4","1","9",".",".","5"],[".",".",".",".","8",".",".","7","9"]] Output: [["5","3","4","6","7","8","9","1","2"],["6","7","2","1","9","5","3","4","8"],["1","9","8","3","4","2","5","6","7"],["8","5","9","7","6","1","4","2","3"],["4","2","6","8","5","3","7","9","1"],["7","1","3","9","2","4","8","5","6"],["9","6","1","5","3","7","2","8","4"],["2","8","7","4","1","9","6","3","5"],["3","4","5","2","8","6","1","7","9"]] Explanation: The input board is shown above and the only valid solution is shown below:
Constraints:
board.length == 9
board[i].length == 9
board[i][j]
is a digit or'.'
.- It is guaranteed that the input board has only one solution.
Solution To the Above Question
class Solution {
public:
//For checking if the input is Valid or not
bool isValid(vector<vector<char>>& board, int row, int col, char c){
int RowNum=(row/3)*3;
int ColNum=(col/3)*3;
for(int i=0; i<9; i++){
if((board[i][col]==c) || (board[row][i]==c) || (board[RowNum+i/3][ColNum+i%3]==c)) {
return false;
}
}
return true;
}
// For Solving the Sudoku
bool solve(vector<vector<char>>& board){
for(int i=0; i<9; i++){
for(int j=0; j<9; 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;
}
}
}
return true;
}
//Main Function
void solveSudoku(vector<vector<char>>& board) {
solve(board);
}
};
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