How do you solve Toggle Light Bulbs on LeetCode?

Toggle Light Bulbs (LeetCode #3842) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Using a set allows efficient toggling.

What is the time complexity of Toggle Light Bulbs?

The optimal solution for Toggle Light Bulbs runs in O(n) time and uses O(n) space. The complexity is O(n) since we only traverse the input array once and use a set for constant time toggling.

What is the brute force solution for Toggle Light Bulbs?

The brute force approach for Toggle Light Bulbs is Brute Force, with O(n²) time complexity and O(1) space complexity. We can simulate the toggling of each bulb directly by iterating through the input array. Each time we encounter a bulb, we check its current state and toggle it. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Toggle Light Bulbs?

Toggle Light Bulbs uses the following concepts: Array, Hash Table, Sorting, Simulation. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Toggle Light Bulbs?

Explain your thought process clearly. Consider edge cases like no bulbs toggled. Discuss time and space complexity upfront.

What are common mistakes when solving Toggle Light Bulbs?

Forgetting to toggle back when a bulb is already on. Not handling the case of multiple toggles correctly.

#3842

Toggle Light Bulbs

Easy

ArrayHash TableSortingSimulationHash MapArray

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

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Intuition

Time O(n)Space O(n)

We can use a set to efficiently track the state of each bulb. This allows for quick toggling and retrieval of the final states.

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Algorithm

3 steps

1Step 1: Initialize an empty set to track the on bulbs.
2Step 2: For each bulb in the input array, toggle its presence in the set.
3Step 3: Return the sorted list of bulbs in the set.

solution.py8 lines

1def toggle_bulbs(bulbs):
2    on_bulbs = set()
3    for bulb in bulbs:
4        if bulb in on_bulbs:
5            on_bulbs.remove(bulb)
6        else:
7            on_bulbs.add(bulb)
8    return sorted(on_bulbs)

ℹ

Complexity note: The complexity is O(n) since we only traverse the input array once and use a set for constant time toggling.

1Using a set allows efficient toggling.
2Sorting the final result is straightforward.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.