LeetCode-Sudoku Solver

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.

简单的回溯搜索即可

class Solution {
public:
    void solveSudoku(vector<vector<char> > &board) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        vector<vector<bool> >check;
        vector<bool> one;
        one.resize(9,false);
        check.resize(27,one);
        vector<vector<int> > empty;
        for(int i=0;i<9;i++){
            for(int j=0;j<9;j++){
                int val=board[i][j]-'1';
                if(val>=0&&val<9){
                    check[i][val]=true;
                    check[9+j][val]=true;
                    check[18+(i/3)*3+j/3][val]=true;
                }
                else{
                    int size=empty.size();
                    empty.resize(size+1);
                    empty[size].push_back(i);
                    empty[size].push_back(j);
                    empty[size].push_back(0);
                }
            }
        }
        int index=0;
        while(true){
            int val=empty[index][2];
            int i=empty[index][0];
            int j=empty[index][1];
            if(val==9){
                //go back
                index--;
                val=empty[index][2];
                i=empty[index][0];
                j=empty[index][1];
                check[i][val]=false;
                check[9+j][val]=false;
                check[18+(i/3)*3+j/3][val]=false;
                empty[index][2]++;
            }
            else{
                if(check[i][val]||check[9+j][val]||check[18+(i/3)*3+j/3][val]){
                    //try next val
                    empty[index][2]++;
                }
                else{
                    check[i][val]=true;
                    check[9+j][val]=true;
                    check[18+(i/3)*3+j/3][val]=true;
                    index++;
                    if(index==empty.size()){
                        //end
                        for(int k=0;k<empty.size();k++){
                            board[empty[k][0]][empty[k][1]]='1'+empty[k][2];
                        }
                        return;
                    }
                    empty[index][2]=0;
                }
            }
        }
    }
};