PPractick

The problem

The second exercise in the pattern series turns the square into a right-angled triangle: the first row has one star, the second has two, and so on until the last row has n. It introduces the single most important idea in pattern problems: the inner loop's bound depends on the row number. Once you see that the number of stars in row i is just i, the change from Pattern 1 is a single character in the code.

Example for n = 4:

*
**
***
****

Function signature

vector<string> rightTriangle(int n);  // row i (1-indexed) has i stars

Test cases

Input n	Output rows	Explanation
1	"*"	One row
3	"*", "**", "***"	Row i has i stars
5	"*", "**", "***", "****", "*****"	Last row has n stars

(Confirm: rows are left-aligned with no leading spaces; stars have no separators.)

How interviewers phrase it

• "Print a right-angled triangle of stars with N rows."
• Often immediately after the square: "Now print a triangle instead."
• A common first question in campus coding tests.

Clarifying questions to ask

1. Left-aligned or right-aligned? (Right-aligned needs leading spaces.)
2. Stars separated by spaces or not?
3. Print directly or return the rows?

Follow-ups to expect

1. "What changed from the square?"
2. "How do you print it right-aligned?"
3. "How many stars in total?"
4. "What's the complexity?"

Related questions

• Easy and Medium Easy
• Hard Easy
• Pattern 1 Easy
• Pattern 3 Easy
• Pattern 4 Easy
• Pattern 5 Easy

All 474 dsa interview questions

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