leetcode@ [36/37] Valid Sudoku / Sudoku Solver

https://leetcode.com/problems/valid-sudoku/

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

A partially filled sudoku which is valid.

Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

class Solution {
public:
    vector<int> getIdx(int i, int j) {
        vector<int> idx(4);
        int row, col;
        if(i>=0 && i<=2) {
            idx[0] = 0; idx[1] = 2;
        }
        else if(i>=3 && i<=5) {
            idx[0] = 3; idx[1] = 5;
        }
        else if(i>=6 && i<=8) {
            idx[0] = 6; idx[1] = 8;
        }
        
        if(j>=0 && j<=2) {
            idx[2] = 0; idx[3] = 2;
        }
        else if(j>=3 && j<=5) {
            idx[2] = 3; idx[3] = 5;
        }
        else if(j>=6 && j<=8) {
            idx[2] = 6; idx[3] = 8;
        }
        
        return idx;
    }
    bool checkRowAndColumn(vector<vector<char>>& board, int i, int j) {
        if(i<0 || i>=board.size() || j<0 || j>=board[0].size()) return false;
        
        for(int ni=0;ni<board.size();++ni) {
            if(ni == i || board[ni][j] == '.') continue;
            if(board[ni][j] == board[i][j]) return false;
        }
        
        for(int nj=0;nj<board[0].size();++nj) {
            if(nj == j || board[i][nj] == '.') continue;
            if(board[i][nj] == board[i][j]) return false;
        }
        
        return true;
    }
    
    bool checkLocal(vector<vector<char>>& board, int i, int j) {
        if(i<0 || i>=board.size() || j<0 || j>=board[0].size()) return false;
        
        vector<int> idx = getIdx(i, j);
        int li = idx[0], ri = idx[1], lj = idx[2], rj = idx[3];
        
        for(int p=li;p<=ri;++p) {
            for(int q=lj;q<=rj;++q) {
                if((i==p && j==q) || board[p][q] == '.') continue;
                if(board[i][j] == board[p][q]) return false;
            }
        }
        
        return true;
    }
    bool isValidSudoku(vector<vector<char>>& board) {
        for(int i=0;i<board.size();++i) {
            for(int j=0;j<board[i].size();++j) {
                if(board[i][j] == '.') continue;
                if(!checkLocal(board, i, j) || !checkRowAndColumn(board, i, j)) return false;
            }
        }
        return true;
    }
};

填写九宫格：

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.

class Solution {
public:
    vector<int> getNext(vector<vector<char>>& board, int x, int y) {
        vector<int> next; next.clear();
        for(int j=y;j<board[0].size();++j) {
            if(board[x][j] == '.') {
                next.push_back(x); next.push_back(j);
                return next;
            }
        }
        for(int i=x+1;i<board.size();++i) {
            for(int j=0;j<board[i].size();++j) {
                if(board[i][j] == '.') {
                    next.push_back(i); next.push_back(j);
                    return next;
                }
            }
        }
        return next;
    }
    vector<int> getIdx(int i, int j) {
        vector<int> idx(4);
        int row, col;
        if(i>=0 && i<=2) {idx[0] = 0; idx[1] = 2;  }
        else if(i>=3 && i<=5) {idx[0] = 3; idx[1] = 5;  }
        else if(i>=6 && i<=8) {idx[0] = 6; idx[1] = 8;  }
        
        if(j>=0 && j<=2) {idx[2] = 0; idx[3] = 2;  }
        else if(j>=3 && j<=5) {idx[2] = 3; idx[3] = 5;  }
        else if(j>=6 && j<=8) {idx[2] = 6; idx[3] = 8;  }
        
        return idx;
    }
    bool checkRowAndColumn(vector<vector<char>>& board, int i, int j) {
        if(i<0 || i>=board.size() || j<0 || j>=board[0].size()) return false;
        
        for(int ni=0;ni<board.size();++ni) {
            if(ni == i || board[ni][j] == '.') continue;
            if(board[ni][j] == board[i][j]) return false;
        }
        
        for(int nj=0;nj<board[0].size();++nj) {
            if(nj == j || board[i][nj] == '.') continue;
            if(board[i][nj] == board[i][j]) return false;
        }
        
        return true;
    }
    
    bool checkLocal(vector<vector<char>>& board, int i, int j) {
        if(i<0 || i>=board.size() || j<0 || j>=board[0].size()) return false;
        
        vector<int> idx = getIdx(i, j);
        int li = idx[0], ri = idx[1], lj = idx[2], rj = idx[3];
        
        for(int p=li;p<=ri;++p) {
            for(int q=lj;q<=rj;++q) {
                if((i==p && j==q) || board[p][q] == '.') continue;
                if(board[i][j] == board[p][q]) return false;
            }
        }
        
        return true;
    }
    
    bool dfs(vector<vector<char>>& board, vector<vector<char>>& res, int x, int y) {
        vector<int> next = getNext(board, x, y);
        if(next.empty()) {
            return true;
        }
        
        int nx = next[0], ny = next[1];
        for(int nn = 1; nn <= 9; ++nn) {
            board[nx][ny] = nn + '0';
            if(checkLocal(board, nx, ny) && checkRowAndColumn(board, nx, ny)) {
                if(dfs(board, res, nx, ny)) {
                    res[nx][ny] = nn + '0';
                    return true;
                }
            }
        }
        return false;
    }
    void solveSudoku(vector<vector<char>>& board) {
        vector<vector<char> > res = board;
        dfs(board, res, 0, 0);
        
        board = res;
    }
};