Printing alphabet pyramid in C - c

Question

I'm trying to write a program in C that gives a 13 row pyramid with the following output (notice the pattern of the letters i.e BCB):
A
BCB
DEFED
GHIJIHG
KLMNONMLK
PQRSTUTSRQP
VWXYZABAZYXWV
CDEFGHIJIHGFEDC
KLMNOPQRSRQPONMLK
TUVWXYZABCBAZYXWVUT
DEFGHIJKLMNMLKJIHGFED
OPQRSTUVWXYZYXWVUTSRQPO
ABCDEFGHIJKLMLKJIHGFEDCBA
Here is my attempt at the solution:
#include <stdio.h>
#include <stdlib.h>
int main(void){
char c = 'A';
int height = 13;
int max = 1;
for (int i = 1; i <= height; i++){
//int j = 1;
for (int k = 0; k < height - i; k++)
printf(" "); // print space on left
for (int j = 1; j <= max; j++){
if (j <= max / 2){ // print left side of pyramid
printf ("%c", c);
c = (c - 'A' + 1) % 26 + 'A';
}
else{ // print right side of pyramid
printf ("%c", c);
c = (c -'A' + 25) % 26 + 'A';
}
}
printf("\n");
max += 2;
}
}
However it gives the following incorrect output:
A
ZAZ
YZAZY
XYZAZYX
WXYZAZYXW
VWXYZAZYXWV
UVWXYZAZYXWVU
TUVWXYZAZYXWVUT
STUVWXYZAZYXWVUTS
RSTUVWXYZAZYXWVUTSR
QRSTUVWXYZAZYXWVUTSRQ
PQRSTUVWXYZAZYXWVUTSRQP
OPQRSTUVWXYZAZYXWVUTSRQPO
if I remove the the if/else statement which splits the pyramid in to two sides and simply have only c = (c - 'A' + 1) % 26 + 'A';, I get the following output:
A
BCD
EFGHI
JKLMNOP
QRSTUVWXY
ZABCDEFGHIJ
KLMNOPQRSTUVW
XYZABCDEFGHIJKL
MNOPQRSTUVWXYZABC
DEFGHIJKLMNOPQRSTUV
WXYZABCDEFGHIJKLMNOPQ
RSTUVWXYZABCDEFGHIJKLMN
OPQRSTUVWXYZABCDEFGHIJKLM
Any ideas?

Answer 1

The problem is that you're forgetting to increment the actual overall character. For each line, you need to add characters until you get to the value that you should start at for the next line. Thankfully, this is pretty easy to do:
...
max += 2;
c = (c - 'A' + max / 2 + 1) % 26 + 'A'; // Add this line
}

Answer 2

Here's a short version:
#include <stdio.h>
#define HEIGHT 6
int main(void) {
char* f = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char* b = "ZYXWVUTSRQPONMLKJIHGFEDCBA";
int c = 0;
for(int i=0; i<HEIGHT; ++i)
{
printf("%*.*s%.*s\n", 10, i+1, f+i+c, i, b+strlen(b)-(c+2*i));
c+=i;
}
return 0;
}
IDEOne Link
Output:
Success #stdin #stdout 0s 9424KB
A
BCB
DEFED
GHIJIHG
KLMNONMLK
PQRSTUTSRQP