Sudoku input data generator

.cpp

#include <iostream>
#include <ctime>
#include <stdlib.h>
#include <vector>


using namespace std;


class Solution {
public:

    bool findFreePos(vector< vector<char> >& board, int& x, int& y) {
        for(x = 0; x < 9; x++)
            for(y = 0; y < 9; y++)
                if(board[x][y] == '.')
                    return true;

        return false;
    }

    bool canSet(vector< vector<char> >& board, int x, int y, char c) {
        for(int i = 0; i < 9; i++)
            if(board[x][i] == c)
                return false;

        for(int i = 0; i < 9; i++)
            if(board[i][y] == c)
                return false;

        for(int i = (x/3)*3; i < (x/3)*3 + 3; i++)
            for(int j = (y/3)*3; j < (y/3)*3 + 3; j++)
                if(board[i][j] == c)
                    return false;

        return true;
    }

    bool solve(vector< vector<char> >& board) {
        int x, y;

        if(!findFreePos(board, x, y))
            return true;

        for(char i = '1'; i <= '9'; i++)
            if(canSet(board, x, y, i)) {
                board[x][y] = i;
                if(solve(board))
                    return true;
                board[x][y] = '.';
            }

        return false;
    }

    void solveSudoku(vector< vector<char> >& board) {
        solve(board);
    }
};

const int MAX_COUNT = 65;
const int MIN_COUNT = 40;


int main(void) {
    srand(time(0));

    Solution s;
    vector<vector<char>> m(9, vector<char>(9, '.'));

    // fill first row with random
    vector<int> v;
    for(int i = 1; i <= 9; i++)
        v.push_back(i);

    for(int i = 0; i < 9; i++) {
        int index = rand() % v.size();
        m[0][i] = v[index] + '0';
        v.erase(v.begin() + index);
    }

    // solve sudoku
    s.solveSudoku(m);

    // erase some cells
    vector< pair<int, int> > filledCells;
    for(int i = 0; i < 9; i++)
         for(int j = 0; j < 9; j++)
             filledCells.push_back(make_pair(i, j));

     int countToDelete = random() % (MAX_COUNT - MIN_COUNT) + MIN_COUNT;
     for(int i = 0; i < countToDelete; i++) {
         int index = rand() % filledCells.size();
         int x = filledCells[index].first;
         int y =filledCells[index].second;
         filledCells.erase(filledCells.begin() + index);

         m[x][y] = '.';
     }

     // print result
     for(int i = 0; i < 9; i++) {
         for(int j = 0; j < 9; j++)
             cout << m[i][j] << " ";
         cout << endl;
     }

    return 0;
}