Difference of Two Arrays | Find What's Unique in O(n) | LeetCode 75 #20

Find the Difference of Two Arrays — LeetCode 2215 (Easy) — explained from zero in Hindi. Given two arrays nums1 and nums2, return two lists: the numbers that are only in nums1, and the numbers that are only in nums2 — each number exactly once. We solve it with two unordered_sets: O(1) membership tests, automatic dedup, O(n+m) time. What you will learn: What "difference of two arrays" really means (with a two-class-lists analogy) A Venn-diagram dry run: every number classified live into its zone The duplicate trap: why we loop over the SET, never the raw array C++ line by line: unordered_set, find(), push_back — with the WHY for every line 6 edge cases, a plain-words correctness proof, and complexity with reasoning Problem: https://leetcode.com/problems/find-th... This is video #20 of the LeetCode 75 series in Hindi — one problem, fully animated, beginner-first. #LeetCode75 #DSAinHindi #CodingInterview #Placements #Cpp #DataStructures #LearnToCode #LeetCode