37. Sudoku Solver

Jingwei Wang answered on May 3, 2023 Popularity 4/10 Helpfulness 1/10

answer 37. Sudoku Solver

37. Sudoku Solver

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boolean backtrack(char[][] board, int r, int c) {
    int m = 9, n = 9;
    if (c == n) {
        // 穷举到最后一列的话就换到下一行重新开始。
        return backtrack(board, r + 1, 0);
    }
    if (r == m) {
        // 找到一个可行解，触发 base case
        return true;
    }
    // 就是对每个位置进行穷举
    for (int i = r; i < m; i++) {
        for (int j = c; j < n; j++) {

            if (board[i][j] != '.') {
                // 如果有预设数字，不用我们穷举
                return backtrack(board, i, j + 1);
            } 

            for (char ch = '1'; ch <= '9'; ch++) {
                // 如果遇到不合法的数字，就跳过
                if (!isValid(board, i, j, ch))
                    continue;

                board[i][j] = ch;
                // 如果找到一个可行解，立即结束
                if (backtrack(board, i, j + 1)) {
                    return true;
                }
                board[i][j] = '.';
            }
            // 穷举完 1~9，依然没有找到可行解，此路不通
            return false;
        }
    }
    return false;
}

boolean isValid(char[][] board, int r, int c, char n) {
    // 见上文
}

Popularity 4/10 Helpfulness 1/10 Language whatever

Source: mp.weixin.qq.com

Tags: solver sudoku whatever

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Contributed on May 03 2023

Jingwei Wang

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