https://www.interviewbit.com/problems/sudoku/

InterviewBit : Sudoku

bool isfine(vector<vector<int>>& res,int x,int y, int no){
    
    int i,j,k;
    
    for( i = 0; i < 9 ; i++ ){
        
        if(res[x][i]==no || res[i][y]==no){
            return false;
        }
        
    }
    
    for(i=(x/3)*3;i<((x/3)*3)+3;i++){
        
        for(j=(y/3)*3;j<((y/3)*3)+3;j++){
            
            if(res[i][j]==no){
                return false;
            }   
            
        }
        
    }
    
    
    
    return true;
}



bool sudoku(int xi,int yi, vector<vector<int>>& res){
    
    if(yi==9){
        yi = 0;
        xi = xi + 1;
        //cout << xi << endl;
    }
    
    if(xi>=9){
        return true;
    }
    
    int i,j;
    
    for(i=xi;i<res.size();i++){
        
        for(j=yi;j<res.size();j++){
            
            if(res[i][j]==0){
                
                for(int k = 1; k <= 9; k++){
                    
                    if(isfine(res,i,j,k)){
                        
                        res[i][j] = k;
                        bool done = sudoku(i,j+1,res);
                        
                        if(done){
                            return true;
                        }   
                        
                        res[i][j] = 0;
                    }
                    
                }
                
                
            }
            
            if(res[i][j]==0){
                return false;
            }
            
        }
        
        yi = 0;
        
    }
 
 return true;   
}





void Solution::solveSudoku(vector<vector<char> > &A) {
    
    vector<vector<int>> res(A.size(),vector<int>(A[0].size(),0));
    
    int i,j;
    
    for(i=0;i<A.size();i++){
        
        for(j=0;j<A[i].size();j++){
            
            if(A[i][j]!='.'){
                res[i][j] = A[i][j] - 48;
            }
            
        }
        
    }
    
    sudoku(0,0,res);
    
    for(i=0;i<A.size();i++){
        
        for(j=0;j<A[i].size();j++){
            A[i][j] = res[i][j] + 48;
        }
        
    }
    
    
}