A right-aligned sequential alphabet pyramid prints a continuous letter stream (A, then B C, then D E F, …) into width-2 cells, with empty cells on the left for alignment.
Remember
Rule: pad width-2 cells, then next letters via k++ (never reset)
A
B C
D E F
G H I J
K L M N O ← 5 rows (15 letters A–O)
Unlike Program 13 (same running counter, left-aligned), this pattern uses fixed-width cells so the pyramid sits on the right in monospace output.
Approach
How to Solve It
Scan a fixed number of width-2 slots per row: print empty cells first, then advance a shared letter counter.
Method
Idea
Best for
Fixed-width scan
Inner $j from n..1; pad if $j > $i else $k++
Learning one-loop alignment
Explicit pad
Print $n - $i empty cells, then $i letters
Clearer reading once the shape is clear
Pseudocode
Pseudocode
$k = 'A'
for $i from 1 to $n:
for $j from $n down to 1:
if $j > $i:
echo two spaces
else:
echo $k in width 2
$k = next letter
echo PHP_EOL
Cheat sheet
Goal
Pattern
Row count
for ($i = 1; $i <= $n; $i++)
Scan slots
for ($j = $n; $j >= 1; $j--)
Empty cell
echo " "; when $j > $i
Letter cell
echo $k++ . " ";
Explicit pad
for ($s = 0; $s < $n - $i; $s++) echo " ";
End the row
echo PHP_EOL;
A–Z-safe height
Cap so $n($n+1)/2 <= 26 (max 7 rows)
Printing Letters vs Starting a New Line
API
Effect
Use for
echo
Stays on the same line
Each empty cell and each letter cell
echo PHP_EOL
Ends the current line
After the fixed-width scan
Print cells without a newline, then end the row once.
Try it
Live Preview
Change the row count and the sequential pyramid updates instantly — including letter totals and last letter.
Whole numbers from 1 to 6. Total letters = n(n+1)/2 (stays within A–U here).
Live result5 rows · 15 letters · ends O
A
B C
D E F
G H I J
K L M N O
Trace
Worked Walkthrough — $n = 4
Trace each row’s pad count, how many letters print, and where the shared counter lands.
Row $i
Pads
Letters
$k range
Printed row
1
3
1
A
A
2
2
2
B C
B C
3
1
3
D E F
D E F
4
0
4
G H I J
G H I J
Total letters: 1 + 2 + 3 + 4 = 10 = n(n+1)/2. Never reset $k between rows or the sequence restarts at A.
Code
PHP Programs
Three complete programs: fixed 5 rows, CLI row-count input, and an explicit pad-then-letters form. Use View Output to reveal sample results.
Example 1 — Fixed 5 Rows
A single counter $k increments only when a letter is printed, and each letter cell is the character plus a trailing space so columns stay width 2.
2. Then letters. Print exactly $i letters via $k++ — same continuous sequence.
3. Same visual. Both still use width-2 cells so the pyramid matches the scan version.
Edge Cases & Pitfalls
Check these before calling the solution done.
Reset $k
Wrong letters
Resetting $k each row restarts at A every line. Keep one counter outside the outer loop.
One space
Misaligned columns
Padding with a single space breaks width-2 alignment. Empty cells must be " " to match letter-plus-space cells.
No pads
Left-aligned
Skipping the pad branch left-aligns the sequential rows — you lose the right-aligned pyramid.
$n = 1
Single A
Output is just A (no pads) — a good sanity check.
Past Z
Clamp letter budget
More than 7 rows needs more than 26 letters. Cap $n or define a wrap rule.
Bad input
Use is_numeric
Casting non-numeric input to int becomes 0. Prefer is_numeric so empty or letter input does not silently fail.
Analysis
Time and Space Complexity
Program
Time
Extra space
Scan / explicit pad forms
O(n²)
O(1)
Each of $n rows scans $n width-2 slots (or pads + letters totaling O(n)). Letters printed equal n(n+1)/2.
Remember
Key Takeaways
Running counter: one $k walks the alphabet across every row — do not reset it.
Width-2 cells: pad with " " and print each letter as $k . " ".
Right align: empty cells first, then the next $i letters.
Complexity:O(n²) time; O(1) extra space.
One line: for each row, pad width-2 cells then echo the next letters from a continuous counter.
Frequently Asked Questions
Because k is not reset inside the outer loop. Each time a letter is printed we use k++ so the sequence continues A, then B C, then D E F, and so on.
Each letter is printed as the character plus a trailing space (two columns). Two spaces keep empty cells the same width so columns align.
Decide a rule: stop at Z, wrap back to A, or switch to a longer alphabet list. Then apply it when incrementing k.
echo stays on the same line for each cell. echo PHP_EOL ends the row after the fixed-width scan finishes.
Program 13 also uses a running letter counter, but prints left-aligned without fixed-width padding. This pattern right-aligns by printing empty 2-column cells first.
O(n²) for n rows when each row scans n slots in the inner loop.
Use trim(fgets(STDIN)) and check is_numeric($input) before casting to int, require n ≥ 1, and cap so n(n+1)/2 ≤ 26 if you want only A–Z letters.
Yes. Print n − i empty width-2 cells, then i letters via k++. Example 3 on this page shows that style.
🤔
Did you know?
Each slot is 2 columns wide. Padding uses " " and letters use echo $k++ . " " (letter then space) so columns line up in monospace output. The counter k never resets, so letters run continuously from A to O for 5 rows.
