Added Missing Description for Find Median from Data Stream

Author: ryanoneill

src/find_median_from_data_stream.rs

@@ -1,5 +1,22 @@
 use std::{collections::BinaryHeap, cmp::Reverse};
 
+/// 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.
 struct MedianFinder {
     min_heap: BinaryHeap<Reverse<i32>>,
     max_heap: BinaryHeap<i32>