Reverse integers above 199

I am solving a problem in C which reverses the integer provided to it.

Code:

int reverse(int x) {
    int i, t = 1, y = 0, neg = 0;
    if (x < 0) {
        neg = 1;
        x = -1 * x;
    }
    while (x / t > 1) {
        t = t * 10;
    }
    int p = t;
    while (t >= 1) {
        int d = x / t;
        y = y + p * d / t;
        x = x - d * t;
        t = t / 10;
    }
    if (neg == 1) {
        y = -1 * y;
    }
    return y;
}

For some reason the program works incorrectly if x is over 199.

In the first while loop, it takes d as 0, and hence an extra 0 is added to the end of the reversed integer.

I know I can just code it to divide by 10 if the input is over 200, but why it happens and is there any alternate solution possible?

Solution

The problem is in the statement:

while(x/t>1)

You are raising y more than the power that suits your algorithm.

It should work if you change the condition like this:

while(x/t>=10)

And here is an alternate solution, which is way simpler than what you're trying to do.

Steps:

1 - Extract the first digit to the right.
2 - Multiply it by 10 and add it to your reversed variable, as if you're pushing it to the left.
3 - Divide your number by 10 to remove the digit you just used.
4 - Repeat until your number is equal to 0.

long reverse_modified(long number)
{
    long rem =0 , reversed = 0;

    /*4*/while (number != 0) 
    {
        /*1*/rem = number % 10;
        /*2*/reversed = reversed * 10 + rem;
        /*3*/number /= 10;
    }
    
    return reversed;
}