PPractick

The problem

This triangle prints alternating 1s and 0s, and the value each row starts with alternates too: odd-numbered rows start with 1, even-numbered rows start with 0. Every row then flips between 1 and 0. It's a small exercise in deriving a cell's value from its position, or tracking a value you toggle as you go, instead of printing a constant or a counter.

Example for n = 5:

1
0 1
1 0 1
0 1 0 1
1 0 1 0 1

Function signature

vector<string> binaryTriangle(int n);  // row i starts with 1 if i is odd, 0 if even; then alternates

Test cases

Input n	Output rows	Explanation
1	"1"	Row 1 starts with 1
2	"1", "0 1"	Row 2 starts with 0
4	"1", "0 1", "1 0 1", "0 1 0 1"
5	as in the example	Every row ends with 1

(Confirm: space-separated with no trailing space; some judges omit the spaces.)

How interviewers phrase it

• "Print a 0-1 triangle where rows alternate their starting digit."
• "Print this binary pattern for N."

Clarifying questions to ask

1. Does row 1 start with 1?
2. Space-separated or not?
3. Print or return?

Follow-ups to expect

1. "Can you compute each value directly instead of toggling?"
2. "Why does every row end with 1?"
3. "What's the complexity?"

Related questions

• Easy and Medium Easy
• Hard Easy
• Pattern 1 Easy
• Pattern 2 Easy
• Pattern 3 Easy
• Pattern 4 Easy

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