Why is my lab1 code failing to pass one test in check50?

Question

First, let me share my code:

int main(void)
{
    int x = 1, y, n = 0, year;
    do
    {
        x = get_int("Enter the starting population size: ");   // TODO: Prompt for start size
    }
    while (x<9);

    do
    {
        y = get_int("Enter the ending population size: ");   // TODO: Prompt for end size
    }
    while (y<x);

    do
    {
        year = x + (x/3) - (x/4);   // TODO: Calculate number of years until we reach threshold
        n++;
        x = year;
    }
    while (year < y);

    printf("Years: %i\n", n);    // TODO: Print number of years
}

Results for cs50/labs/2021/x/population generated by check50 v3.1.2
:) population.c exists
:) population.c compiles
:) handles starting values less than 9
:) handles ending values less than starting values
:) handles decimal number of llamas
:( handles same starting and ending sizes
    expected "Years: 0", not "Years: 1\n"
:) handles starting population of 1200
:) rejects invalid populations and then handles population 9
:) rejects invalid populations and then handles population 20
:) handles starting population of 100

Why is it failing the test: :( handles same starting and ending sizes expected "Years: 0", not "Years: 1\n"?

Answer 1

It's failing the test because you are using a do-while loop which is incrementing n before it checks if year < y. Remember that the reason to use a do-while loop instead of a while loop is that you can ensure that the code block is executed at least once, regardless of the condition.