## 🧠 Solving LeetCode Until I Become Top 1% — Day `41`

🔹 Problem: 3439 Reschedule Meetings for Maximum Free Time I

Difficulty: #Medium
Tags: #Greedy, #SlidingWindow, #Intervals

📝 Problem Summary

Given a timeline and a bunch of meetings that don’t overlap (how convenient), you're allowed to reschedule up to k of them. You can’t change their order or duration, only shift them around to create as much free time as possible. Return the length of the longest uninterrupted block of free time you can manufacture.

🧠 My Thought Process

Brute Force Idea:
I didn’t even reach this stage. My brain just threw a 503 error. Everything looked like a heap problem, or maybe a job scheduler from the future. I started thinking about binary search trees and forgot what I was solving. Fantastic start.
Optimized Strategy:
After reading the discussion (aka being rescued by the brave souls who solved it), I found out it’s actually a sliding window over “gaps between meetings”. If I merge k+1 of these gaps, I can “simulate” shifting k meetings out of the way and combine the in-between free time.

Okay... sure. That makes sense now.

Algorithm Used: [[Sliding_Window]] disguised as a scheduling problem. The trick is to compute all the gaps, then apply a moving sum of k+1 to simulate the best-case meeting reshuffles.

⚙️ Code Implementation (Python)

class Solution:
    def maxFreeTime(self, eventTime, k, startTime, endTime):
        n = len(startTime)
        gaps = [startTime[0]]
        for i in range(1, n):
            gaps.append(startTime[i] - endTime[i - 1])
        gaps.append(eventTime - endTime[-1])

        window = sum(gaps[:k+1])
        ans = window

        for i in range(k+1, len(gaps)):
            window += gaps[i] - gaps[i - (k+1)]
            ans = max(ans, window)

        return ans

⏱️ Time & Space Complexity

Time: O(n)
Space: O(n)

🧩 Key Takeaways

✅ Sliding window is versatile — even when your brain isn’t.
💡 When a problem says “maximize free time,” don’t overthink. Just try merging gaps.
💭 This is like Merge Intervals meets Max Subarray Sum meets Why am I doing this at 2 AM.

🔁 Reflection (Self-Check)

[ ] Could I solve this without help?
→ Absolutely not. It was like my brain called in sick for the day.
[ ] Did I write code from scratch?
→ Eventually, yes... with the training wheels of LeetCode discussions on full display.
[x] Did I understand why it works?
→ Now I do. Took me a hot minute, though.
[x] Will I be able to recall this in a week?
→ If my ego survives this problem, sure.