Concatenation of first letter alike regardless of upper and lower case in C

Question

i have been figuring out how to combine strings that has first same letter alike regardless of their cases. I have a code that if you input

babe,two,Bird,Tea

the output is always like this

babe,Bird,Tea,two

But the input that I want to see is like this

babeBird,Teatwo

What am i going to add or change in my code in order for me to do that. Here's my code:

#include<stdio.h>
#include<string.h>
#include <ctype.h>

int main()
{
char str1[1000][1000], str[1000], temp[1000];
int n, i, p, j, a;
char *ptr, *ptr1, letter;


printf("Enter how many arrays: ");
scanf("%d", &n);

for(i=0; i<n; i++)
{
    printf("Enter string %d: ", i+1);
    scanf("%s", &str1[i]);
}

for(i=0; i<n-1; i++)
{
    for(j=i+1; j<n; j++)
    {
    if (tolower((unsigned char)str1[i][0]) == tolower((unsigned char)str1[j][0])
   ){
       strcpy(temp, str1[i]);
       strcpy(str1[i], str1[j]);
       strcpy(str1[j], temp);
    }
   if(strcasecmp(str1[i], str1[j])>0)
   {
       strcpy(temp, str1[i]);
       strcpy(str1[i], str1[j]);
       strcpy(str1[j], temp);
     }
   }
}

 for(i=0; i<n; i++)
  {
  if (i != 0)
    {
    else if (str1[i][0] != letter)
    {
        printf(",");
    }
  }


    {
printf("%s", str1[i]);
letter = str1[i][0];
    }
  }
}

Answer 1

The following code which decides whether to print a comma

if (str1[i][0] != letter)

does a case-sensitive comparison.

Change it to something like

if (tolower(str1[i][0]) != tolower(letter))

However, the code contains multiple bugs (too many to point them all out), so not sure it will work. You might want to do debugging.