有哪位可以解读这个代码

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define ROW 9
#define COL 9
#define CORRECT 0
#define WRONG -1 
#define MAXNUM 1000 /*数独游戏个数*/  
#define SEED 20171212/*用于随机数生成的种子*/ 
int checkSudoku(const char a[][COL]) /*按规则检查函数*/
{
    int i, j, x, y;
    for (i = 0; i < ROW; i++) {
        for (j = 0; j < COL; j++) {
            for (x = 0; x < COL; x++)
                if (a[i][x] == a[i][j] && x != j)
                    return WRONG;

            for (x = 0; x < ROW; x++)
                if (a[x][j] == a[i][j] && x != i)
                    return WRONG;

            for (x = i / 3 * 3; x < i / 3 * 3 + 3; x++)
                for (y = j / 3 * 3; y < j / 3 * 3 + 3; y++)
                    if (a[x][y] == a[i][j] && (x != i && y != j))
                        return WRONG;
        }
    }
    return CORRECT;
}
void printSudoku(const char a[][COL]) /*打印数独到屏幕*/
{
    int i, j;
    printf("\n ┌───——─┬───——─┬——────┐\n");
    for (i = 0; i < ROW; i++) {
        if (i != 0 && i % 3 == 0) printf(" ├────——┼——────┼─——───┤\n");
        printf(" │");
        for (j = 0; j < COL; j++) {
            if (j != 0 && j % 3 == 0) printf("  │");
            if (a[i][j])
                printf(" %c", a[i][j]);
            else printf("  ");
        }
        printf("  │\n");
    }
    printf(" └─——───┴───——─┴——────┘\n");
}
void readFromFile(char a[][COL], const char filename[]) /*从文件中读取数独*/
{
    // To Be Solved
    // 从文件filename中读取到的数独初盘存储到数组a[][COL]中
    int i = 0, j = 0, num = 81;
    char c = 0;
    FILE *fp = fopen(filename, "r");//读文件 

    while (num)
    {
        fscanf(fp, "%c", &c);
        if (c == 10 || c == 32)
        {
            continue;
        }
        a[i][j] = c;
        num--;
        j++;
        if (j >= 9)
        {
            j = 0;
            i++;
        }
    }
    fclose(fp);
}

int Solve(char arr[ROW][COL], int row, int col)/*封装后的解数独函数*/
{
    int i, j;
    char n = 48;
    int flag_next = 0;

    int next_row = 0, next_col = 0;

    while (1) {
    next_num:
        ++n;
        if (n > 57) break;

        // 判断行重复
        for (j = 0; j < ROW; j++) {
            if (arr[row][j] == n) {
                goto next_num;
            }
        }

        // 判断列重复
        for (i = 0; i < COL; i++) {
            if (arr[i][col] == n) {
                goto next_num;
            }
        }

        /* 判断所在小九宫格重复*/
        int x = (row / 3) * 3;
        int y = (col / 3) * 3;
        for (i = x; i < x + 3; i++) {
            for (j = y; j < y + 3; j++) {
                if (arr[i][j] == n) {
                    goto next_num;
                }
            }
        }

        //该单元可以填充
        arr[row][col] = n;
        //如果9宫格已填满，完成，这里不考虑有多解的情况
        flag_next = 0;
        for (i = 0; i < ROW; i++)
            for (j = 0; j < COL; j++)
                if (arr[i][j] == '0') {
                    next_row = i;
                    next_col = j;
                    flag_next = 1;
                    break;
                }
        if (!flag_next)
        {
            return 1;
        }
        //否则继续填下一个未填充的格子
        if (!Solve(arr, next_row, next_col)) {
            //数独填写完毕就不重写以前留下的足迹
            arr[row][col] = 48;
            continue;//一直到本次循环完毕，直接跳出循环后，执行最后的 return 0;
        }
        else
            return 1;//成功的标志，一路返回
    }
    /*flag_next = 0;
        for (i = 0; i < ROW; i++)
            for (j = 0; j < COL; j++)
                if (arr[i][j] == '0') {
                    next_row = i;
                    next_col = j;
                    flag_next = 1;
                    break;
                }
    if(!flag_next)
        return 0;
    else
        Solve(arr, next_row, next_col);*/
    return 0;
}
void solveSudoku(const char a[][COL], char b[][COL]) {
    // To Be Solved 
    // 参数const char a[][COL]表示初盘二维数组；
    // 参数char b[][COL]表示解的二维数组。 
    int row = 0, col = 0;
    int flag=0;
    for (int i = 0;i < ROW;i++) {
        for (int j = 0;j < COL;j++)
        {
            b[i][j] = a[i][j];
        }
    }
    for (int i = 0; i < ROW; i++)
        for (int j = 0; j < COL; j++)
            if (b[i][j] == '0') {
                row = i;
                col = j;
                flag=1;
                break;
            }
    Solve(b, row, col);
            /*
    while(flag)
    {
        Solve(b, row, col);
        flag=0;
        for (int i = 0; i < ROW; i++)
        for (int j = 0; j < COL; j++)
        {
            if (b[i][j] == '0') {
                row = i;
                col = j;
                flag=1;
                break;
            }
        }
    }*/
}
int main() {
    char starting_grid[ROW][COL] = { 0 };
    char result[ROW][COL] = { 0 };
    char filename[50];
    int rr = 0;
    double time_from, time_to, time_sum = 0;
    int i = 0;
    for (i = 873; i < MAXNUM; i++) {
        sprintf(filename, "sudoku\\%04d.txt", i);
        readFromFile(starting_grid, filename);
        printf("\n\n             *%4d  *", i);
        printSudoku(starting_grid);
        time_from = clock();
        solveSudoku(starting_grid, result);
        time_to = clock();
        time_sum += time_to - time_from;
        printSudoku(result);
        rr = checkSudoku(result);
        if (rr == WRONG) {
            printf("Something goes wrong...\n");
            return WRONG;
        }
        else printf("            Correct!!!\n");
        printf("  ==============================");
    }
    printf("\n Congretulations! ToTal Time:%fs\n", time_sum / CLOCKS_PER_SEC);
    return 0;
}