Solving Leetcode Daily 301. Remove Invalid Parentheses in Python

Solving Leetcode Daily 301. Remove Invalid Parentheses in Python | Backtracking & Optimization In this video, we tackle LeetCode 301 - Remove Invalid Parentheses in Python. We walk step-by-step through designing a Backtracking algorithm, analyzing decision trees, encountering bugs live, and adding key pruning optimizations to improve performance. 📌 Problem Link: https://leetcode.com/problems/remove-... ⏱️ Timestamps 0:00 - Problem Statement & Constraints 1:28 - Complexity Estimation (2^20 Decision Tree) 3:03 - Designing the Backtracking State (bt function) 5:49 - Implementing Recursive Branching Logic 9:46 - Base Case & Initializer Setup 12:25 - Live Debugging: Fixing Output Errors 16:32 - Optimization 1: Remaining Character Bound Check (left less open) 17:53 - Optimization 2: Global Minimum Removals Pruning 19:11 - Code Refactoring & Parameter Cleanup 22:02 - Optimization 3: Accumulator List Optimization (append/pop) 24:04 - Comparing DFS vs BFS & Community Solutions 🧠 Key Concepts & Approach At every index, we decide whether to keep or remove the current bracket: ✹ Keep ( / ): Append to accumulator, adjust open bracket tracking, and recurse. ✹ Remove ( / ): Increment removed count without appending, and recurse. ✹ Non-Brackets: Always keep and move to the next index. ⚡ Pruning Optimizations: ✹ Suffix Balance Check: If the remaining characters in string s are fewer than the current count of open brackets (len(s) - I less than open), it is impossible to close all open brackets. We prune early. ✹ Global Minimum Tracking: If removed count exceeds our current best global minimum (g_removed at 0), we stop searching down this sub-optimal branch. 📊 Complexity ✹Time Complexity: O(2 ^N) upper bound, heavily reduced in practice by pruning bounds. ✹Space Complexity: O(N) for call stack frame depth and accumulator tracking. 💻 Python Implementation https://leetcode.com/problems/remove-... #leetcode #daily #algorithms #faang #interview #backtracking