Binary Search And Sorting

3 problems in this category

Binary Search Two Pointers Divide and Conquer Sorting

Binary Search

Search in sorted array of integers and return index if target is found.

Easy LeetCode
Time:
O(log n)?
Why O(log n)?
We halve the search space each iteration
Each comparison eliminates half of the remaining elements. We can eliminate at most log₂(n) halves.
Example: Array of 1000 elements needs max 10 comparisons (2¹⁰ = 1024)
Space:
O(1)?
Why O(1)?
Only using a few variables
We only store left, right, and mid pointers - constant space regardless of input size.
Example: Same memory usage for array of 10 or 10,000 elements
Example: nums = [-1,0,3,5,9,12], target = 9 → 4
Binary Search
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Find First and Last Position

Find the starting and ending position of a given target value.

Medium LeetCode
Time: O(log n)
Space: O(1)
Example: nums = [5,7,7,8,8,10], target = 8 → [3,4]
Binary Search Two Pointers
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Merge Sort

Sort an array using Merge Sort algorithm.

Medium LeetCode
Time: O(n log n)
Space: O(n)
Example: [5,2,3,1] → [1,2,3,5]
Divide and Conquer Sorting
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