The object of this C Win32 application is to find a multiple of 9 with its digits summing to a multiple of 9 also. The first column below is a multiple of 9 whose digits sum to 9 also. The second column is the sum of digits found in the column one number. The last column is the first column divided by 9.
Enter PRNG seed:
1
Enter number of bits (4 to 16):
4
9 9 1
Enter number of bits (4 to 16):
5
27 9 3
Enter number of bits (4 to 16):
6
45 9 5
Enter number of bits (4 to 16):
7
117 9 13
Enter number of bits (4 to 16):
8
252 9 28
Enter number of bits (4 to 16):
0
C:\Users\james\source\repos\CProductOf9Console\Debug\CProductOf9Console.exe (process 23280) exited with code 0.
Press any key to close this window . . .
Enter PRNG seed:
1
Enter number of bits (4 to 16):
9
369 18 41
Enter number of bits (4 to 16):
10
846 18 94
Enter number of bits (4 to 16):
11
1080 9 120
Enter number of bits (4 to 16):
12
3015 9 335
Enter number of bits (4 to 16):
13
5040 9 560
Enter number of bits (4 to 16):
14
10350 9 1150
Enter number of bits (4 to 16):
15
30870 18 3430
Enter number of bits (4 to 16):
16
57798 36 6422
Enter number of bits (4 to 16):
0
// CProductOf9Console.c (c) Sunday, June 23, 2024
// by James Pate Williams, Jr., BA, BS, MSwE, PhD
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char nextStr[256], numbStr[256];
void ConvertToString(int number, int radix)
{
int i = 0;
while (number > 0)
{
nextStr[i++] = (char)(number % radix + '0');
number /= radix;
}
nextStr[i++] = '\0';
_strrev(nextStr);
}
int Sum(int next)
{
long sum = 0;
ConvertToString(next, 10);
for (int i = 0; i < (int)strlen(nextStr); i++)
sum += (long)nextStr[i] - '0';
if (sum % 9 == 0 && sum != 0)
return sum;
return -1;
}
long GetNext(int numBits, int* next)
{
long hi = 0, lo = 0, nine = 0;
nextStr[0] = '\0';
numbStr[0] = '\0';
if (numBits == 4)
{
while (1)
{
*next = 9 * (long)(rand() % 16);
if (*next != 0 && *next >= 8 && *next < 16)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 5)
{
while (1)
{
*next = 9 * (long)(rand() % 32);
if (*next >= 16 && *next < 32)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 6)
{
while (1)
{
*next = 9 * (long)(rand() % 64);
if (*next >= 32 && *next < 64)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 7)
{
while (1)
{
*next = 9 * (long)(rand() % 128);
if (*next >= 64 && *next < 128)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 8)
{
while (1)
{
*next = 9 * (long)(rand() % 256);
if (*next >= 128 && *next < 256)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 9)
{
while (1)
{
*next = 9 * (long)(rand() % 512);
if (*next >= 256 && *next < 512)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 10)
{
while (1)
{
*next = 9 * (long)(rand() % 1024);
if (*next >= 512 && *next < 1024)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 11)
{
while (1)
{
*next = 9 * (long)(rand() % 2048);
if (*next >= 1024 && *next < 2048)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 12)
{
while (1)
{
*next = 9 * (long)(rand() % 4096);
if (*next >= 2048 && *next < 4096)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 13)
{
while (1)
{
*next = 9 * (long)(rand() % 8192);
if (*next >= 4096 && *next < 8192)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 14)
{
while (1)
{
*next = 9 * (long)(rand() % 16384);
if (*next >= 8192 && *next < 16384)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 15)
{
while (1)
{
*next = 9 * (long)(rand() % 32768);
if (*next >= 16384 && *next < 32768)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
else if (numBits == 16)
{
while (1)
{
*next = 9 * (long)(rand() % 65536);
if (*next >= 32768 && *next < 65536)
{
nine = Sum(*next);
if (nine % 9 == 0)
return nine;
}
}
}
return -1;
}
int main()
{
char buffer[256] = { '\0' };
long seed = 0;
printf_s("Enter PRNG seed:\n");
scanf_s("%s", buffer, sizeof(buffer));
seed = atol(buffer);
srand((unsigned int)seed);
while (1)
{
int next = 0, nine = 0, numberBits = 0;
printf_s("Enter number of bits (4 to 16):\n");
scanf_s("%s", buffer, sizeof(buffer));
numberBits = atol(buffer);
if (numberBits == 0)
break;
if (numberBits < 4 || numberBits > 16)
{
printf_s("illegal number of bits must >= 4 and <= 16\n");
continue;
}
nine = GetNext(numberBits, &next);
if (nine == -1)
{
printf_s("illegal result, try again\n");
continue;
}
printf_s("%5ld\t%5ld\t%5ld\n", next, nine, next / 9);
}
return 0;
}
Numerical Explorations 