Overview
Two pointers technique: sorted array pe do pointers se O(n) mein solve karo jo brute force O(n^2) leta.
Analogy
Jaise rope ke dono ends se tighten karo — ek end se chhodo, dusre end se uthao.
Step-by-step
- Left pointer start pe, right pointer end pe
- Condition ke hisaab se left ya right move karo
- Jab left >= right ho toh stop karo
Visual
arr = [1,2,3,4,5,6], target=7
left=0(1), right=5(6) -> sum=7 found!
Common mistakes
- Sorted array assume karna zaroor — unsorted pe kaam nahi karta
- Pointer update karna bhool jaana — infinite loop
- left < right condition use karo (not <=)
Practice questions
- Two sum in sorted array solve karo
- Container with most water solve karo