Đổi số sang chữ

#include <stdio.h>
#include <string.h>
#include <conio.h>
#define Max 101
#define printp printf(" "); //in khoang trang
#define printd printf("\n");//xuong dong
#define printdonvi printf(" (VND)");
//co the thay VND bang don vi tien te khac (i.e USD, EUR)


void printc(char c); //Ham in ra chu tuong ung voi so
void num2vitext(char s[], int n); //Ham chuyen so thanh chu (Viet khong dau)
int chuanhoa(char s[]);
int bang0(char s[]);


int main()
{
    char t[Max];
    char ex = 'Y';

    while (ex != 27)
    {
        system("cls");
        printf("Nhap so tien (dang so): ");
        fflush(stdin);
        gets(t);
        printf("========================================\n");
        if (!chuanhoa(t))
            printf("Du lieu khong hop le!");
        else
        {
            printf("So tien (dang chu) la: ");
            num2vitext(t, strlen(t));
            printdonvi;
        }
        printf("\n========================================\n");
        printf("Nhan ESC de thoat, Enter de tiep tuc: ");
        ex = getch();
    }
    return 0;
}

void printc(char c)
{
    switch (c)
    {
        case '0': printf("khong"); break;
        case '1': printf("mot"); break; //laf mootj chuws khoong phair moots
        case '2': printf("hai"); break;
        case '3': printf("ba"); break;
        case '4': printf("bon"); break;
        case '5': printf("nam"); break;
        case '6': printf("sau"); break;
        case '7': printf("bay"); break;
        case '8': printf("tam"); break;
        case '9': printf("chin"); break;
    }
    return;
}

void num2vitext(char s[], int n)
{
    //Neu chi co mot chu so, in ra binh thuong
    if (n == 1)
    {
        printc(s[0]);
        return;
    }
    //Neu co 2 chu so
    if (n == 2)
    {
        if (s[0] == '1') printf("muoi");
        else
        {
            printc(s[0]);
            printf(" muoi");
        }
        //---------------------------------
        if (s[1] == '0') return;
        else
        if (s[1] == '5') printf(" lam");
        else
        if (s[1] == '4')
        {
            if (s[0] >= '2') printf(" tu");
            else
            {
                printp;
                printc(s[1]);
            }
        }
        else
        if (s[1] == '1')
        {
            if (s[0] == '1')
            {
                printp;
                printc(s[1]);
            }
            else printf(" mot"); //moots
        }
        else
        {
            printp;
            printc(s[1]);
        }
        return;
    }
    //Neu co 3 chu so
    if (n == 3)
    {
        printc(s[0]);

        printf(" tram");
        //----------------------------------------
        if (s[1] == '0')
        {
            if (s[2] == '0') return;
            else
            {
                printf(" le ");
                printc(s[2]);
            }
        }
        else
        {
            char s0[3];
            memmove(s0, s+1, 2);
            printp;
            num2vitext(s0, 2);
        }
        return;
    }
    //Neu tu 10 chu so tro len, tach ra thanh cac nhom co 9 so
    if (n > 9)
    {
        char s1[n - 9 + 1], s2[9 + 1];
        memmove(s1, s, n - 9);
        memmove(s2, s + n - 9, 9);
        num2vitext(s1, n-9);
        printf(" ti ");
        num2vitext(s2, 9);
        return;
    }

    if (n > 3)
    {
        char s3[4], s4[7];
        if (n > 6)
        {
            memmove(s3, s, n-6);
            memmove(s4, s+n-6, 6);
            if (bang0(s3));
            else
            {
                num2vitext(s3, n-6);
                printf(" trieu");
            }
            if (!bang0(s4))
            {
                printp;
                num2vitext(s4, 6);
            }
        }

        if (n <= 6)
        {
            memmove(s3, s, n-3);
            memmove(s4, s+n-3, 3);
            if (bang0(s3));
            else
            {
                num2vitext(s3, n-3);
                printf(" nghin");
            }
            if (!bang0(s4))
            {
                printp;
                num2vitext(s4, 3);
            }
        }
        return;
    }
    else
    printf("\nCo loi xay ra!?");
    return;
}
int chuanhoa(char s[])
{
    if (s[0] == '\0') return 0;
    if (s[0] == '0') return 0;
    int i;
    for (i = 0; i < strlen(s); i++)
        if ((s[i] <48) || (s[i] > 57)) return 0;

    return 1;
}

int bang0(char s[])
{
    int i;
    for (i = 0; i < strlen(s); i++)
        if (s[i] != '0') return 0;
    return 1;
}