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SudokuSolver.java
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SudokuSolver.java
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package gracefulsoul.problems;
import gracefulsoul.util.PrintUtil;
public class SudokuSolver {
// https://leetcode.com/submissions/detail/495130327/
public static void main(String[] args) {
SudokuSolver test = new SudokuSolver();
char[][] board = new char[][] {
new char[] { '5', '3', '.', '.', '7', '.', '.', '.', '.' },
new char[] { '6', '.', '.', '1', '9', '5', '.', '.', '.' },
new char[] { '.', '9', '8', '.', '.', '.', '.', '6', '.' },
new char[] { '8', '.', '.', '.', '6', '.', '.', '.', '3' },
new char[] { '4', '.', '.', '8', '.', '3', '.', '.', '1' },
new char[] { '7', '.', '.', '.', '2', '.', '.', '.', '6' },
new char[] { '.', '6', '.', '.', '.', '.', '2', '8', '.' },
new char[] { '.', '.', '.', '4', '1', '9', '.', '.', '5' },
new char[] { '.', '.', '.', '.', '8', '.', '.', '7', '9' }
};
test.solveSudoku(board);
PrintUtil.print(board);
}
public void solveSudoku(char[][] board) {
if (board == null || board.length == 0) {
return;
}
this.solve(board);
}
private boolean solve(char[][] board) {
for (int i = 0; i < board.length; i++) {
for (int j = 0; j < board[i].length; j++) {
if (board[i][j] == '.') {
for (char c = '1'; c <= '9'; c++) {
if (this.isValid(board, i, j, c)) {
board[i][j] = c;
if (this.solve(board)) {
return true;
} else {
board[i][j] = '.';
}
}
}
return false;
}
}
}
return true;
}
private boolean isValid(char[][] board, int row, int col, char c) {
for (int i = 0; i < 9; i++) {
if (board[i][col] != '.' && board[i][col] == c ||
board[row][i] != '.' && board[row][i] == c ||
(
board[3 * (row / 3) + i / 3][3 * (col / 3) + i % 3] != '.' &&
board[3 * (row / 3) + i / 3][3 * (col / 3) + i % 3] == c
)
) {
return false;
}
}
return true;
}
}