DSA in Java #8 | Trapping Rain Water: from O(n²) to O(n) time and O(1) space

DSA in Java: Episode 8 of SyntaxPilot's free DSA full course, with real-life examples for every concept. Trapping Rain Water: from O(n²) to O(n) time and O(1) space. In this video you'll learn: • The problem, with a real-life example • Water on one bar = min(left max, right max) - height • Brute force: scan both sides for every bar, and why it gets TLE • Prefix max and suffix max arrays: O(n) time, O(n) space • Two pointers: why the smaller side is already decided, O(1) space • The overflow bug on big inputs, and the long fix • The exclusive-max bug: negative water • Time and space complexity of all three solutions Every concept starts with a real-life example, then an animation and notes, then live code in the SyntaxPilot online compiler. Practice free in the SyntaxPilot compiler (nothing to install): https://syntaxpilot.in/ Detailed notes for this episode (code, outputs, practice): https://claude.ai/artifact/3NFFnpsgo1... Interactive animations: https://claude.ai/artifact/G8didLNQmc... Chapters 00:00 Welcome 00:22 Today's agenda 00:45 Rain in the courtyard 01:42 Water on ONE tower 02:20 Brute force, and the time limit 04:07 Left max, right max arrays 06:24 Two pointers, O(1) space 07:56 Typed live, edge cases 09:29 Overflow and negative water 11:00 Complexity 11:22 Quick quiz 11:48 Recap and homework 12:19 Next episode Next episode: Sliding window: longest substring without repeating characters Post your homework and quiz answer in the comments, and subscribe for the full basic-to-master playlist, free. #DSA #DSATutorial #SyntaxPilot