Pattern 18
EasyTriangle of trailing letters
Problem
Print an alphabet triangle of trailing letters for a given size n.
Use one loop for the rows and another for what goes in each row to draw the shape.
The idea
Each row ends at the same final letter and starts further back as the rows grow, so the starting letter is what changes. Work out the first letter of the row and then count forwards.
The trick
- Row i starts at 'A' + (n - i) and runs to 'A' + (n - 1).
rows5
Step 1 of 7. Trailing letters: row i prints the last i letters up to E. rows 5.
1/7
Optimal
timeO(n^2)spaceO(1)
1// n = 5 produces:2// E3// D E4// C D E5// B C D E6// A B C D E7 8for i in 1..n:9 for j in (n-i)..(n-1): print(char('A'+j))10 newlineInput
- grid
- 5 × 5
Memory
- rows
- 5
Output
- printed rows
- —
- rows
- 5
Check yourself
3 quick questions about this walkthrough. A wrong answer costs nothing.
Example
- Input:
- n = 5
- Output:
- E / D E / C D E / B C D E / A B C D E
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