PPractick

The problem

This pattern keeps the triangle shape but changes what is printed once more: every entry in row i is the number i itself. So row 1 is 1, row 2 is 2 2, row 3 is 3 3 3. Placed next to Pattern 3, it shows exactly the difference between printing a value that depends on the column (1, 2, 3...) and one that depends on the row (the same number repeated). Interviewers often ask both back to back to see whether you understand what each loop variable represents.

Example for n = 4:

1
2 2
3 3 3
4 4 4 4

Function signature

vector<string> repeatedNumberTriangle(int n);  // row i: i repeated i times, space-separated

Test cases

Input n	Output rows	Explanation
1	"1"	One row
3	"1", "2 2", "3 3 3"	Row i repeats i, i times
5	"1", "2 2", "3 3 3", "4 4 4 4", "5 5 5 5 5"

(Confirm: numbers are space-separated with no trailing space; some judges print them without spaces.)

How interviewers phrase it

• "Print a triangle where row i contains the number i repeated i times."
• Often paired with Pattern 3: "Now print the row number instead of the column number."

Clarifying questions to ask

1. Space-separated or not?
2. Trailing spaces allowed?
3. Print or return?

Follow-ups to expect

1. "What's the one change from Pattern 3?"
2. "How would you print the sum of each row?"
3. "What's the complexity?"

Related questions

• Easy and Medium Easy
• Hard Easy
• Pattern 1 Easy
• Pattern 2 Easy
• Pattern 3 Easy
• Pattern 5 Easy

All 474 dsa interview questions

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