add solution and links from problem-253

Author: curtisbarnard

README.md

@@ -108,6 +108,7 @@ In order to practice with similar data structures I'll be placing each problem i
 - [Merge Intervals #56](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/medium/merge-intervals-56.md)
 - [Evaluate Reverse Polish Notation #150](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/medium/polish-notation-150.md)
 - [Maximum Units on a Truck #1710](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/easy/max-units-truck-1710.md)
+- [Meeting Rooms II](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/medium/meeting-rooms-ii-253.md)
 
 ### Queue
 
@@ -166,6 +167,7 @@ In order to practice with similar data structures I'll be placing each problem i
 ### Heap
 
 - [K Closest Points to Origin #973](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/medium/k-closest-origin-973.md)
+- [Meeting Rooms II](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/medium/meeting-rooms-ii-253.md)
 
 ## Algorithm Patterns
 
@@ -180,6 +182,7 @@ Within the problems above there are several patterns that often occur. I plan to
 - [Middle of the Linked List #876](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/easy/middle-linked-list-876.md)
 - [Contains Duplicate #217](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/easy/contains-duplicate-217.md)
 - [3Sum #15](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/medium/3Sum-15.md)
+- [Meeting Rooms II](https://github.com/curtisbarnard/leetcode-grind75-javascript/blob/main/medium/meeting-rooms-ii-253.md)
 
 ### Sliding Window
 

medium/meeting-rooms-ii-253.md

@@ -0,0 +1,59 @@
+# Meeting Rooms II
+
+Page on leetcode: https://leetcode.com/problems/meeting-rooms-ii/
+
+## Problem Statement
+
+Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), find the minimum number of conference rooms required.)
+
+### Constraints
+
+### Example
+
+```
+Input: intervals = [(0,30),(5,10),(15,20)]
+Output: 2
+Explanation:
+We need two meeting rooms
+room1: (0,30)
+room2: (5,10),(15,20)
+```
+
+## Solution
+
+### Optimized Solution
+
+This problem can be approached using sorting and two pointers or using a heap. The below is with a heap which has a time complexity of O(nlogn) and space complexity of O(n). You can see an explanation of this approach here: https://www.youtube.com/watch?v=qx7Akat3xrM
+
+```javascript
+const minMeetingRooms(intervals) {
+  // Sort meetings by start times
+  intervals.sort((a,b) => a[0] - b[0])
+
+  // Create initial heap
+  const usedRooms = [intervals[0][1]]
+
+  // iterate thru meetings and compare start times to heap
+  for (let i = 1; i < intervals.length; i++){
+    // If current meeting has no overlap with the minheap meeting, then remove the minheap meeting. We won't need an additional meeting room.
+    if (intervals[i][0] >= usedRooms[0]) {
+      heapifyDown()
+    }
+    // Add current meeting to the heap
+    heapifyUp(intervals[i][1])
+  }
+
+  return usedRooms.length
+
+  // Heapify Up helper
+  function heapifyUp(endTime) {
+
+  }
+
+  // Heapify Down helper
+  function heapifyDown(endTime) {
+
+  }
+
+}
+```