Merge pull request neetcode-gh#2052 from kiryl-labada/main

Update 0295-find-median-from-data-stream.cs. Use heap solution

csharp/0295-find-median-from-data-stream.cs

@@ -1,23 +1,40 @@
 public class MedianFinder {
+ private PriorityQueue<int, int> leftHeap = new(Comparer<int>.Create((a, b) => b - a));
+ private PriorityQueue<int, int> rightHeap = new();
 
- List<int> Nums;
  public MedianFinder() {
 
- Nums = new List<int>();
  }
 
+ // T: log(n)
  public void AddNum(int num) {
- int index = Nums.BinarySearch(num);
- if (index < 0)
- {
- index = ~index; 
- } 
- Nums.Insert(index, num);
+ if (leftHeap.Count == 0 || num > leftHeap.Peek()) 
+ rightHeap.Enqueue(num, num);
+ else 
+ leftHeap.Enqueue(num, num);
+
+ Balance();
+ }
+
+ private void Balance() {
+ var (big, small) = leftHeap.Count > rightHeap.Count
+ ? (leftHeap, rightHeap)
+ : (rightHeap, leftHeap);
+
+ while (big.Count - small.Count > 1) {
+ var value = big.Dequeue();
+ small.Enqueue(value, value);
+ }
  }
 
+ // T: O(1)
  public double FindMedian() {
- int count = Nums.Count;
- return count % 2 == 0 ? (double)((Nums[count / 2 - 1] + Nums[count / 2]) * 0.5) : Nums[count / 2];
+ if (leftHeap.Count == rightHeap.Count) 
+ return (leftHeap.Peek() + rightHeap.Peek()) / 2.0;
+
+ return leftHeap.Count > rightHeap.Count
+ ? leftHeap.Peek()
+ : rightHeap.Peek(); 
  }
 }
 
@@ -26,59 +43,4 @@ public double FindMedian() {
  * MedianFinder obj = new MedianFinder();
  * obj.AddNum(num);
  * double param_2 = obj.FindMedian();
- 
- // ***IMP : Not passing for few test cases 
- class MedianFinder
- {
-
- private PriorityQueue<int, int> smallHeap; //small elements - maxHeap
- private PriorityQueue<int, int> largeHeap; //large elements - minHeap
-
- public MedianFinder()
- {
- smallHeap = new PriorityQueue<int, int>();
- largeHeap = new PriorityQueue<int, int>();
- }
-
- public void addNum(int num)
- {
- smallHeap.Enqueue(num, num);
- if (
- smallHeap.Count - largeHeap.Count > 1 ||
- !(largeHeap.Count <= 0) &&
- smallHeap.Peek() > largeHeap.Peek()
- )
- {
- if (smallHeap.Count > 0)
- {
- int ele = smallHeap.Dequeue();
- largeHeap.Enqueue(ele, ele);
- }
- }
- if (largeHeap.Count - smallHeap.Count > 1)
- {
- if (largeHeap.Count > 0)
- {
- int ele = largeHeap.Dequeue();
- smallHeap.Enqueue(ele, ele);
- }
- }
- }
-
- public double findMedian()
- {
- if (smallHeap.Count == largeHeap.Count)
- {
- return (double)(largeHeap.Peek() + smallHeap.Peek()) / 2;
- }
- else if (smallHeap.Count > largeHeap.Count)
- {
- return (double)smallHeap.Peek();
- }
- else
- {
- return (double)largeHeap.Peek();
- }
- }
- }
  */