Pattern 2
EasyLeft-aligned right triangle
Problem
Print a left-aligned right triangle of stars 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
Row i prints i stars, so the inner loop's bound depends on the outer counter rather than being fixed. That single change — inner bound tied to the row number — turns the square into a triangle.
The trick
- Row i (1-based) has exactly i stars, so the inner loop runs `j <= i`.
- Total stars printed is 1+2+…+n = n(n+1)/2, so the work is O(n²).
rows5
Step 1 of 7. Right triangle: row i prints i stars. rows 5.
1/7
Optimal
timeO(n^2)spaceO(1)
1// n = 5 produces:2// *3// * *4// * * *5// * * * *6// * * * * *7 8for i in 1..n:9 for j in 1..i: print('* ')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:
- ★ / ★ ★ / ★ ★ ★ / ★ ★ ★ ★ / ★ ★ ★ ★ ★
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