验证Sudoku广场

我需要帮助弄清楚什么问题以及如何修复它。我正在尝试制作一个程序，以验证Sudoku董事会是否有效。我已经检查了是否有效，是否有效，但是正方形验证是我正在努力的地方。这是我的代码：

#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include <pthread.h>
using namespace std;
int *board[9];
int row, col;
void *is_row_ok(void *param);
void *is_col_ok(void *param);
void *is_square_ok(void *param);
int main()
{
    for (int i = 0; i < 9; ++i)
    {
        board[i] = new int[9];
    }
    string line;
    ifstream myFile("Testfile3.txt");
    for (int row = 0; row < 9; ++row)
    {
        string line;
        getline(myFile, line);
        stringstream iss(line);
        cout << endl;
        for (int col = 0; col < 9; ++col)
        {
           string val;
           getline(iss, val, ',');
           if (!iss.good())
                break;
            stringstream convertor(val);
            convertor >> board[row][col];
            cout << board[row][col] << "  ";
        }
    }
    pthread_t thread1;
    pthread_t thread2;
    pthread_t thread3;
    pthread_create(&thread1, NULL, is_row_ok, NULL);
    pthread_create(&thread2, NULL, is_col_ok, NULL);
    pthread_create(&thread3, NULL, is_square_ok, NULL);
    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);
    pthread_join(thread3, NULL);
    cout << endl;
    return 0;
 }
void *is_col_ok(void *param)
{
    int element_count = 0;
    char element_value;
    for (int i = 0; i < 9; ++i)
    {
        for (int j = 0; j < 9; ++j)
        {
            element_count = 0;
            element_value = board[i][j];
            if (element_value != ' ')
            {
                for (int k = 0; k < 9; ++k)
                {
                    if (board[k][j] == element_value)
                        element_count++;
                }
            }
            if (element_count >= 2)
            {
                cout << "Column " << j << " is invalid." << endl;
                break;
            }
            else
            {
                cout << "Column " << j << " is valid." << endl;
            }
        }
    }
    pthread_exit(NULL);
}
void *is_square_ok (void *param)
{
    int square = 0;
    int element_count = 0;
    char element_value;
    for (int m = 0; m < 9; m+3)
    {
        for (int n = 0; n < 9; n+3)
        {
            for (int i = m; i < m+3; i++)
            {
                for (int j = n; j < n+3; j++)
                {
                    element_count = 0;
                    element_value = board[i][j];
                    if (element_value != ' ')
                    {
                        for (int k = m; k < m+3; k++)
                        {
                            for (int l = n; l < n+3; l++)
                            {
                                if (board[k][l] == element_value)
                                    element_count++;
                            }
                        }
                    }
                }
            }
        }
        square++;
        if (element_count >= 2)
        {
            cout <<"Square " << square << " is invalid." << endl;
        }
        else
        {
            cout <<"column " << square << " is valid." << endl;
        }
    }
    pthread_exit(NULL);
}

我故意省略了行检查功能，因为这很好。如果有人可以帮助我弄清楚如何修复我的正方形检查功能，这将不胜感激。

P.S。如果有人可以看一下我的列检查功能，并查看我只能打印出一次列验证的方式，那也将非常有用。目前，它由于外循环而相信9次的每一列验证。

预先感谢您。