LeetCode-in-All

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.

Implement the MedianFinder class:

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:

Follow up:

Solution

class MedianFinder
  def initialize()
    @arr = []
  end

=begin
    :type num: Integer
    :rtype: Void
=end
  def add_num(num)
    placement = @arr.bsearch_index {|a| num < a}

    if placement.nil?
      @arr << num
    elsif placement == 0
      @arr.unshift(num)
    else
      @arr.insert(placement, num)
    end
  end

=begin
    :rtype: Float
=end
  def find_median()
    if @arr.size % 2 == 0
      mid = @arr.size / 2
      (@arr[mid] + @arr[mid - 1]).fdiv(2)
    else
      mid = @arr.size / 2
      @arr[mid]
    end
  end
end

# Your MedianFinder object will be instantiated and called as such:
# obj = MedianFinder.new()
# obj.add_num(num)
# param_2 = obj.find_median()