PPractick

The problem

The alpha hill is a centred pyramid of letters where each row climbs from A up to the row's peak letter and back down: A, ABA, ABCBA. It reuses the star pyramid's spacing (n − i leading spaces, 2i − 1 characters) but fills the characters with a palindrome instead of stars. It's a nice test of whether you can combine a known shape with a new content rule, and of handling the "peak" character exactly once.

Example for n = 4:

   A
  ABA
 ABCBA
ABCDCBA

Function signature

vector<string> alphaHill(int n);  // row i: n - i spaces, then A..(i-th letter)..A

Test cases

Input n	Output rows	Explanation
1	"A"
2	" A", "ABA"
3	" A", " ABA", "ABCBA"	Peak letter appears once per row
4	as in the example	Row i has 2i − 1 letters

(Confirm: 1 ≤ n ≤ 26; leading spaces for centring, no trailing spaces.)

How interviewers phrase it

• "Print the alpha hill pattern for N."
• "Print a pyramid of letters where each row is a palindrome."

Clarifying questions to ask

1. N at most 26?
2. Trailing spaces allowed?
3. Print or return?

Follow-ups to expect

1. "How is this related to the star pyramid?"
2. "How do you make sure the peak letter isn't repeated?"
3. "Can you compute each character from its position?"
4. "Complexity?"

Related questions

• Easy and Medium Easy
• Hard Easy
• Pattern 1 Easy
• Pattern 2 Easy
• Pattern 3 Easy
• Pattern 4 Easy

All 474 dsa interview questions

DSA mock interviews · System design interview questions · Free mock interview practice · Browse interviewers · Sign in