Insert Delete GetRandom O(1) Explained | LeetCode 380 C#

Master LeetCode 380, Insert Delete GetRandom O(1), with a visual C# walkthrough of RandomizedSet. Learn how a List plus Dictionary enables uniform random selection, and how the swap-with-last trick removes any value without shifting elements. In this episode: Define the RandomizedSet contract Combine a dense list with a value-to-index dictionary Implement average O(1) Insert and GetRandom See why removing directly from the middle is O(n) Derive swap-with-last removal step by step Walk through the official LeetCode example Read the complete C# implementation Review time and space complexity Chapters: 0:00 The RandomizedSet goal 0:27 Insert, Remove, and GetRandom contract 0:59 One set, two data structures 1:34 Insert in average O(1) 2:10 Uniform GetRandom 2:46 Pause and solve the removal challenge 3:21 Why RemoveAt(index) is too slow 3:49 Swap-with-last walkthrough 4:28 Why changing order is safe 4:57 Official LeetCode example 5:40 C# state and Insert 6:09 C# Remove 6:45 C# GetRandom and complexity 7:13 The pattern to remember Recall challenge: after copying the last value into the removed value's slot, which mapping must be repaired? #LeetCode #CSharp #DataStructures Tags leetcode 380, insert delete getrandom o1, insert delete getrandom o(1), randomizedset, randomized set c#, leetcode c#, leetcode explained, data structures, hash table, dictionary c#, list c#, swap with last, coding interview, top interview 150, solution quest