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🧠

Name things for the reader, not the writer.

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Open the command palette to jump anywhere
Browse blogs and courses by track
Try the live code playground

🧠

Name things for the reader, not the writer.

Tips & tricks

Open the command palette to jump anywhere
Browse blogs and courses by track
Try the live code playground

Language

Runs in the browser · readline() reads stdin

Explorer

Single Number (XOR)

solution.ts

Single Number (XOR)

easy⏱ 15 mintypescriptchallengesproblem-solving-basic-

Exampleinput → output

Input

5
4 1 2 1 2

Output

Sample case — your program reads stdin and prints to stdout.

Given a non-empty array where every element appears twice except for one, find that single element.

Use XOR: a ^ a = 0, a ^ 0 = a. XOR all numbers together.

Example: [4,1,2,1,2] → 4 (1^1=0, 2^2=0, 4^0=4)

Input format Line 1: n. Line 2: n space-separated integers.

Output format The single number.

Constraints 1 ≤ n ≤ 3×10⁴, n is odd

Every problem you solve becomes a story you can tell in an interview.

Solving under pressure trains the muscle that's most tested in onsite rounds.
Explaining your approach out loud matters more than reaching the optimal solution.
Consistency wins: 1 challenge daily > 10 challenges on one Saturday a month.

Pro tip:After solving, write 2 lines on what you learned — that's what you'll remember in the interview.

mainIdle

solution.ts

🧠

Name things for the reader, not the writer.

Tips & tricks

Open the command palette to jump anywhere
Browse blogs and courses by track
Try the live code playground

Language

Runs in the browser · readline() reads stdin

Explorer

Single Number (XOR)

solution.ts

Single Number (XOR)

easy⏱ 15 mintypescriptchallengesproblem-solving-basic-

Exampleinput → output

Input

5
4 1 2 1 2

Output

Sample case — your program reads stdin and prints to stdout.

Given a non-empty array where every element appears twice except for one, find that single element.

Use XOR: a ^ a = 0, a ^ 0 = a. XOR all numbers together.

Example: [4,1,2,1,2] → 4 (1^1=0, 2^2=0, 4^0=4)

Input format Line 1: n. Line 2: n space-separated integers.

Output format The single number.

Constraints 1 ≤ n ≤ 3×10⁴, n is odd

Every problem you solve becomes a story you can tell in an interview.

Solving under pressure trains the muscle that's most tested in onsite rounds.
Explaining your approach out loud matters more than reaching the optimal solution.
Consistency wins: 1 challenge daily > 10 challenges on one Saturday a month.

Pro tip:After solving, write 2 lines on what you learned — that's what you'll remember in the interview.

mainIdle

solution.ts

Optimus Agency | Professional Web Development