Calculation of 4 digit numbers - c

Question

What I am trying to do in the code below is to to make the input a four-digit number (if it's not already) and then sort the digits in the number in an ascending and descending order. x is ascending, y is descending. Then I want to subtract x and y until I get the result 6174 of the subtraction.
#include <stdio.h>
int main() {
int number, count = 0, digit, pow = 0, result = 1, counter, temp,
x = 0, y = 0, i, j, substract = 0, count1 = 0;
scanf("%d", &number);
while (substract != 6174 && substract >= 0) {
substract = 0;
if (count1 > 0) {
temp = substract;
} else {
temp = number;
}
while (temp > 0) {
digit = temp % 10;
temp = temp / 10;
count++;
}
if (count < 4) {
pow = 4 - count;
/* Calculate base^exponent */
for (counter = 0; counter < pow; counter++) {
result = result * 10;
}
number = number * result;
}
for (i = 9, j = 0; i >= 0 && j <= 9; i--, j++) {
int tmpNumber = number;
while (tmpNumber > 0) {
int digit = tmpNumber % 10;
if (digit == i) {
x *= 10;
x += digit;
} else
if (digit == j) {
y *= 10;
y += digit;
}
tmpNumber /= 10;
}
}
substract = x - y;
count++;
printf("\n x %d", x);
printf("\n y %d", y);
printf("\n substract %d", x - y);
}
return 0;
}
When I input 3542 What I expect as an output is this
input:
3524
output:
x 5432
y 2345
subtract 3087
x 8730
y 0378
subtract 8352
x 8532
y 2358
subtract 6174
But what I get is actually this:
input:
3524
output:
x 5432
y 2345
subtract 3087
x 54325432
y 23452345
subtract 30873087
I think the problem is something with the x and y. I have to reset them to zero at some point. But I don't know where. I've tried every single place in the code. If anyone knows where I do wrong I will really appreciate the help.

Answer 1

The program fails for multiple reasons:
You do not reset x and y to 0 for each iteration
result should also be reset to 1
The initial phase of the loop is too complicated: you should test if substract is 0 or 6174 to stop the loop and store substract to number at the end of the loop.
Here is a simpler version that does not need to make number have 4 digits:
#include <stdio.h>
int main(void) {
int number;
if (scanf("%d", &number) == 1 && number >= 0 && number < 10000) {
for (;;) {
int x = 0, y = 0, substract;
for (int i = 9, j = 0; i >= 0 && j <= 9; i--, j++) {
for (int tmp = number, n = 0; n < 4; n++) {
int digit = tmp % 10;
if (digit == i) {
x *= 10;
x += digit;
} else
if (digit == j) {
y *= 10;
y += digit;
}
tmp /= 10;
}
}
substract = x - y;
printf("x %d\n", x);
printf("y %d\n", y);
printf("substract %d\n", substract);
if (substract == 0 || substract == 6174)
break;
number = substract;
}
}
return 0;
}