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/**

* Median is the middle value in an ordered integer list. If the size of the

* list is even, there is no middle value. So the median is the mean of the two

* middle value.

*

* For example,

* [2,3,4], the median is 3

*

* [2,3], the median is (2 + 3) / 2 = 2.5

*

* Design a data structure that supports the following two operations:

*

* void addNum(int num) - Add a integer number from the data stream to the data structure.

* double findMedian() - Return the median of all elements so far.

*

* Example:

* addNum(1)

* addNum(2)

* findMedian() -> 1.5

* addNum(3)

* findMedian() -> 2

*/

public class FindMedianFromDataStream295 {

class MedianFinder {

private PriorityQueue<Integer> maxQ = new PriorityQueue<>(10, (i1, i2) -> Integer.compare(i2, i1));

private PriorityQueue<Integer> minQ = new PriorityQueue<>();

/** initialize your data structure here. */

public MedianFinder() {

}

public void addNum(int num) {

if (maxQ.size() == 0 && minQ.size() == 0) {

maxQ.add(num);

} else if (maxQ.size() == 0) {

if (minQ.peek() < num) {

minQ.add(num);

} else {

maxQ.add(num);

}

} else {

if (maxQ.peek() > num) {

maxQ.add(num);

} else {

minQ.add(num);

}

}

while (maxQ.size() != 0 && maxQ.size() > minQ.size()) {

minQ.add(maxQ.poll());

}

while (minQ.size() != 0 && maxQ.size() < minQ.size()) {

maxQ.add(minQ.poll());

}

}

public double findMedian() {

if (maxQ.size() == minQ.size()) {

return (maxQ.peek() + minQ.peek()) * 1.0 / 2;

} else if (maxQ.size() > minQ.size()) {

return maxQ.peek();

} else {

return minQ.peek();

}

}

}

class MedianFinder2 {

private PriorityQueue<Integer> maxQ = new PriorityQueue<>(10, (i1, i2) -> Integer.compare(i2, i1));

private PriorityQueue<Integer> minQ = new PriorityQueue<>();

/** initialize your data structure here. */

public MedianFinder() {

}

// slower than previous solution MedianFinder, but code is clearner

public void addNum(int num) {

maxQ.add(num);

minQ.add(maxQ.pop());

while (minQ.size() != 0 && maxQ.size() < minQ.size()) {

maxQ.add(minQ.poll());

}

}

public double findMedian() {

if (maxQ.size() == minQ.size()) {

return (maxQ.peek() + minQ.peek()) * 1.0 / 2;

} else if (maxQ.size() > minQ.size()) {

return maxQ.peek();

} else {

return minQ.peek();

}

}

}

/**

* https://leetcode.com/problems/find-median-from-data-stream/discuss/74119/18ms-beats-100-Java-Solution-with-BST

*/

class MedianFinder3 {

class TreeNode{

int val;

TreeNode parent,left,right;

TreeNode(int val, TreeNode p){

this.val=val;

this.parent=p;

left=null;

right=null;

}

void add(int num){

if(num>=val){

if(right==null)

right=new TreeNode(num,this);

else

right.add(num);

}else{

if(left==null)

left=new TreeNode(num,this);

else

left.add(num);

}

}

TreeNode next(){

TreeNode ret;

if(right!=null){

ret=right;

while(ret.left!=null)

ret=ret.left;

}else{

ret=this;

while(ret.parent.right==ret)

ret=ret.parent;

ret=ret.parent;

}

return ret;

}

TreeNode prev(){

TreeNode ret;

if(left!=null){

ret=left;

while(ret.right!=null)

ret=ret.right;

}else{

ret=this;

while(ret.parent.left==ret)

ret=ret.parent;

ret=ret.parent;

}

return ret;

}

}

int n;

TreeNode root, curr;

// Adds a number into the data structure.

public void addNum(int num) {

if(root==null){

root = new TreeNode(num,null);

curr=root;

n=1;

}else{

root.add(num);

n++;

if(n%2==1){

if(curr.val<=num)

curr=curr.next();

}else

if(curr.val>num)

curr=curr.prev();

}

}

// Returns the median of current data stream

public double findMedian() {

if(n%2==0){

return ((double)curr.next().val+curr.val)/2;

}else

return curr.val;

}

};

class MedianFinder4 {

private PriorityQueue<Integer> left;

private PriorityQueue<Integer> right;

/** initialize your data structure here. */

public MedianFinder() {

left = new PriorityQueue<>((i1, i2) -> Integer.compare(i2, i1));

right = new PriorityQueue<>((i1, i2) -> Integer.compare(i1, i2));

}

public void addNum(int num) {

if (right.size() != 0 && right.peek() < num) {

right.add(num);

if (left.size() < right.size()) {

left.add(right.poll());

}

} else {

left.add(num);

if (left.size() > right.size() + 1) {

right.add(left.poll());

}

}

}

public double findMedian() {

if (left.size() == right.size()) {

return ((double) left.peek() + (double) right.peek()) / 2.0;

} else {

return (double) left.peek();

}

}

}

/**

* Your MedianFinder object will be instantiated and called as such:

* MedianFinder obj = new MedianFinder();

* obj.addNum(num);

* double param_2 = obj.findMedian();

*/

}