Added running median heap problem

Author: anirudherabelly

Data Structures/Heap/RunningMedian/RunningMedian_V1.java

@@ -0,0 +1,80 @@
+/*
+Given an input stream of n integers the task is to insert integers to stream and 
+print the median of the new stream formed by each insertion of x to the stream.
+--------------------------------------------------------------------------------
+Example
+
+Flow in stream : 5, 15, 1, 3 
+5 goes to stream --> median 5 (5)
+15 goes to stream --> median 10 (5, 15)
+1 goes to stream --> median 5 (5, 15, 1)
+3 goes to stream --> median 4 (5, 15, 1, 3)
+
+Input:
+The first line of input contains an integer N denoting the no of elements of the stream. 
+Then the next N lines contains integer x denoting the no to be inserted to the stream.
+
+Output:
+For each element added to the stream print the floor of the new median in a new line.
+
+Constraints:
+1<=N<=10^5+7
+1<=x<=10^5+7
+
+Example:
+Input:
+4
+5
+15
+1 
+3
+Output:
+5
+10
+5
+4
+*/
+import java.util.*;
+import java.lang.*;
+import java.io.*;
+class GFG
+ {
+	public static void main (String[] args)
+	 {
+	 //code
+	 Scanner sc=new Scanner(System.in);
+        int n=sc.nextInt();
+        PriorityQueue<Integer> maxHeap=new PriorityQueue<Integer>(
+            new Comparator<Integer> () {
+                public int compare(Integer a, Integer b) {
+                    return b - a;
+                }   
+            }    
+        );
+        PriorityQueue<Integer> minHeap=new PriorityQueue<Integer>();
+        int first=sc.nextInt();
+        int second=sc.nextInt();
+        if(first<second){
+            maxHeap.add(first);
+            minHeap.add(second);
+        }
+        else{
+            maxHeap.add(second);
+            minHeap.add(first);
+        }
+        System.out.println(first);
+        System.out.println(((first+second))/2);
+        for(int i=0;i<n-2;i++){
+            int t=sc.nextInt();
+            if(t<maxHeap.peek())maxHeap.add(t);
+            else minHeap.add(t);
+            int diff=minHeap.size()-maxHeap.size();
+            if(diff>1)maxHeap.add(minHeap.poll());
+            if(diff<-1)minHeap.add(maxHeap.poll());
+            diff=minHeap.size()-maxHeap.size();
+            if(diff==0)System.out.println((minHeap.peek()+maxHeap.peek())/2);
+            else if(diff==1)System.out.println(minHeap.peek());
+            else System.out.println(maxHeap.peek());
+        }
+	 }
+}

Data Structures/Heap/RunningMedian/RunningMedian_V2.java

@@ -0,0 +1,46 @@
+class MedianFinder {
+    
+    /** initialize your data structure here. */
+    PriorityQueue<Integer> minHeap = new PriorityQueue<Integer>();
+    PriorityQueue<Integer> maxHeap = new PriorityQueue<Integer>(
+        new Comparator<Integer>(){
+            public int compare(Integer a, Integer b){
+                if(a > b)return -1;
+                else if(a == b)return 0;
+                return 1;
+            }
+        }
+    );
+    
+    public MedianFinder() {
+        
+    }
+    
+    public void addNum(int num) {
+        int diff = maxHeap.size()-minHeap.size();
+        if(diff == 0){
+            minHeap.add(num);
+            maxHeap.add(minHeap.poll());    
+        }
+        else{
+            maxHeap.add(num);
+            minHeap.add(maxHeap.poll());    
+        }
+    }
+    
+    public double findMedian() {
+        double median = 0; 
+        int diff = maxHeap.size()-minHeap.size();
+        
+        if(diff==0)median = (maxHeap.peek()+minHeap.peek())/2.0;
+        else median = maxHeap.peek();
+        return median;
+    }
+}
+
+/**
+ * Your MedianFinder object will be instantiated and called as such:
+ * MedianFinder obj = new MedianFinder();
+ * obj.addNum(num);
+ * double param_2 = obj.findMedian();
+ */