Same answer. One takes 1 second. One takes 3 hours.

That difference is Big O

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Constant time

Reading arr[5] takes one step, whether the array has 10 items or 10 million.

One loop

Checking every item once. Twice the data, twice the time.

Loop inside a loop

Comparing every pair. 1,000 items means about a million steps.

Halving

Binary search cuts the range in half each step. A million items take about 20 steps.

The mistake

Counting exact steps. Big O drops constants: 3n + 5 is just O(n).

Can you get it?

Tap an answer. The full video explains why.

Cheat sheet

• O(1): one step
• O(log n): halve each time
• O(n): one loop
• O(n log n): good sorting
• O(n²): loop in a loop

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