g0201_0300.s0295_find_median_from_data_stream

Class MedianFinder

java.lang.Object

g0201_0300.s0295_find_median_from_data_stream.MedianFinder

public class MedianFinder
extends Object

295 - Find Median from Data Stream.

Hard

The median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value and the median is the mean of the two middle values.

• For example, for arr = [2,3,4], the median is 3.
• For example, for arr = [2,3], the median is (2 + 3) / 2 = 2.5.

Implement the MedianFinder class:

• MedianFinder() initializes the MedianFinder object.
• void addNum(int num) adds the integer num from the data stream to the data structure.
• double findMedian() returns the median of all elements so far. Answers within 10-5 of the actual answer will be accepted.

Example 1:

Input

["MedianFinder", "addNum", "addNum", "findMedian", "addNum", "findMedian"]
[[], [1], [2], [], [3], []]

Output: [null, null, null, 1.5, null, 2.0]

Explanation:

MedianFinder medianFinder = new MedianFinder();
medianFinder.addNum(1); // arr = [1]
medianFinder.addNum(2); // arr = [1, 2]
medianFinder.findMedian(); // return 1.5 (i.e., (1 + 2) / 2)
medianFinder.addNum(3); // arr[1, 2, 3]
medianFinder.findMedian(); // return 2.0 

Constraints:

• -105 <= num <= 105
• There will be at least one element in the data structure before calling findMedian.
• At most 5 * 104 calls will be made to addNum and findMedian.

Follow up:

• If all integer numbers from the stream are in the range [0, 100], how would you optimize your solution?
• If 99% of all integer numbers from the stream are in the range [0, 100], how would you optimize your solution?

Constructor Summary

Constructors

Constructor and Description
MedianFinder()

Method Summary

Modifier and Type	Method and Description
void	addNum(int num)
void	balance(PriorityQueue<Integer> maxHeap, PriorityQueue<Integer> minHeap)
double	findMedian()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MedianFinder

public MedianFinder()

Method Detail

addNum

public void addNum(int num)

balance

public void balance(PriorityQueue<Integer> maxHeap,
                    PriorityQueue<Integer> minHeap)

findMedian

public double findMedian()