Find Median from Data Stream

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.

Examples:

[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.

For example:

add(1)

add(2)

findMedian() -> 1.5

add(3)

findMedian() -> 2

The answer is:

Input:

addNum(6),findMedian(),addNum(10),findMedian(),addNum(2),findMedian(),addNum(6),findMedian(),addNum(5),findMedian(),addNum(0),findMedian(),addNum(6),findMedian(),addNum(3),findMedian(),addNum(1),findMedian(),addNum(0),findMedian(),addNum(0),findMedian()

Output:

[6.00000,8.00000,6.00000,6.00000,5.50000,5.00000,5.00000,4.00000,3.00000,3.00000,3.00000]

Expected:

[6.00000,8.00000,6.00000,6.00000,6.00000,5.50000,6.00000,5.50000,5.00000,4.00000,3.00000]

This seems like a wrong answer! Is this a wrong answer?

The last two addNum(0) shold not change the median value, because 0 has been added in the data stream, But the value changed in expected answer. And the answer is wrong from the fifth value.