Printf multiple variable number of strings in C

First, the problem with the code. It is based on an incorrect understanding of printf. printf cannot be used in the way desired in the code. Furthermore, even if did, it wont be printing spaces 'gradually' because you have fixed 'n-1'. You probably meant 'n-i' so it can gradually shrink.

Anyways, to fix: There are a number of solutions, including rewriting with new logic. For your homework though, the code can still be 'fixed' by writing your own printf variant with desired functionality. e.g:

void mprintf(const char *fmt, int n, char c)
{
    while (n--)
   {
       printf("%c", c);
    }
 }

And your code becomes:

for (int i = 0 ; i < n ; i++)
{
    mprintf("%c",n-i,' ');  // printing the blank spaces gradually
    mprintf("%c",i,'#'); // printing the hashes gradually
    printf("\n");
}

Extra credit: Find out how you can simplify this code by removing certain useless thing.

You know every row has the same number of chars, counting the spaces and #, which is n. In the first row you have only one #, so n - 1 spaces, on the second you have 2 #'s, so n - 2 spaces, and so on. So you iterate from 0 to n - 1, and print a char every iteration, and you just have to keep count of how many chars you've already print. Start printing spaces and as soon as you have printed enough spaces, print a #. Code for it:

for (int i = 0 ; i < n ; i++) 
{
    int j = 0;
    while (j < n)
    {
        if (j < n - i - 1)
             printf(" ");
        else
             printf("#");
        j++;
    }
    printf("\n");
}

You say:

Please consider helping me by saying what is wrong with my code, not giving me an actual new working one.

Ignoring cosmetic changes, your loop body is currently:

for (int i = 0; i < n; i++) 
{
    printf("%c", n-1, ' ');    // printing the blank spaces gradually
    printf("%c\n", i+2, '#');  // printing the hashes gradually
}

Problems include:

• Too many arguments to the printf() calls.
• %c requires a single argument, which is the character to be printed.
• For n = 6, you will be printing Control-E rather than any blanks with the first print.
• For the second print, you'll be printing Control-B through Control-G and no hashes.

You could use:

printf("%.*s", n - i - 1, " ");

to print a field of blanks of the appropriate width. You can't repeat a single character with printf(), though, so you'd have to use some other technique, such as a loop using putchar(), to print the appropriate number of hashes.

You should read, and re-read, and re-re-read the specification for printf(). I have to read it a couple of times a year to try and keep current; I usually find something new (or forgotten) on a given re-reading. Of course, I've only been coding in C for 30 years, and the specification has changed a few times over the years (and it hasn't gotten any simpler yet!), so it isn't very surprising.