PPractick

The problem

Next in the series, the triangle shape stays the same, but instead of stars each row prints the numbers from 1 up to the row number. The shape comes from the same row formula as Pattern 2, and the new part is deciding what to print in each position. The question to ask is whether the printed value depends on the row, the column, or both. Here it depends only on the column.

Example for n = 4:

1
1 2
1 2 3
1 2 3 4

Function signature

vector<string> numberTriangle(int n);  // row i: "1 2 ... i", space-separated, no trailing space

Test cases

Input n	Output rows	Explanation
1	"1"	One row
3	"1", "1 2", "1 2 3"	Each row counts from 1 to its row number
5	"1", "1 2", "1 2 3", "1 2 3 4", "1 2 3 4 5"
11	last row "1 2 3 4 5 6 7 8 9 10 11"	Space separators keep two-digit numbers readable

(Confirm: numbers are separated by single spaces with no trailing space; some judges print them without spaces, which only changes the separator.)

How interviewers phrase it

• "Print a triangle where row i contains the numbers 1 to i."
• Asked right after the star triangle: "Now print numbers instead of stars."

Clarifying questions to ask

1. Should numbers be separated by spaces? (Important once N reaches 10.)
2. Are trailing spaces acceptable?
3. Print directly or return the rows?

Follow-ups to expect

1. "What decides the number you print?"
2. "What if each row should repeat the row number instead?"
3. "How do you avoid a trailing space?"
4. "What's the complexity?"

Related questions

• Easy and Medium Easy
• Hard Easy
• Pattern 1 Easy
• Pattern 2 Easy
• Pattern 4 Easy
• Pattern 5 Easy

All 474 dsa interview questions

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