Week 17 of 43
Core DSA
WEEK 17 LEARNING MODULE
Two Pointers Technique
Replaces nested loop $O(n^2)$ brute forces with linear $O(n)$ scans using converging (opposite-direction) and fast-slow (same-direction) pointer patterns.
3 Practice Problems4 Core ConceptsVerified Curriculum: high Confidence
What You'll Learn
- ✓Master Two Pointers to solve search and optimization problems in $O(n)$ time and $O(1)$ space.
- ✓Implement Converging Pointers: moving from left and right boundaries inward (Two Sum II, Container With Most Water).
- ✓Implement Fast-Slow Pointers: modifying arrays in-place while maintaining read/write indices.
- ✓Extend Two Pointers to solve 3Sum in $O(n^2)$ time with duplicate avoidance.
Core Concepts
Two Pointers Paradigm
O(n)Iterating over sequences using two synchronized indices to reduce quadratic search spaces to linear time.
Converging Pointers Pattern
O(n)Left and right pointers starting at opposite array ends, moving inward based on comparison with target.
Greedy Boundary Squeezing
O(n)In Container With Most Water, shifting the shorter line inward because moving the taller line can never increase area.
Duplicate Avoidance in K-Sum
O(n²)Skipping adjacent identical values to ensure unique combinatorial solution sets.
Algorithms Covered
Sorted Array Two Sum ($O(n)$)Container With Most Water Area MaximizationIn-place Array Compaction3Sum Algorithm ($O(n^2)$)
Data Structures Applied
ArraysStrings
“There are no foolish questions, and no man becomes a fool until he has stopped asking questions”
— Charles Proteus Steinmetz