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.

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;
}
}
}
}
};

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