added Find Median from Data Stream (hard)

Author: minhyeong-joe

Hard/FindMedianFromDataStream/Driver.java

@@ -0,0 +1,28 @@
+package Hard.FindMedianFromDataStream;
+
+public class Driver {
+ 
+ public static void main(String[] args) {
+ // Your MedianFinder object will be instantiated and called as such:
+ MedianFinder mf = new MedianFinder();
+ mf.addNum(1);
+ mf.addNum(2);
+ mf.print();
+ System.out.println("Output: " + mf.findMedian());
+ mf.addNum(3);
+ mf.print();
+ System.out.println("Output: " + mf.findMedian());
+ mf.addNum(6);
+ mf.addNum(9);
+ mf.print();
+ System.out.println("Output: " + mf.findMedian());
+ mf.addNum(5);
+ mf.print();
+ System.out.println("Output: " + mf.findMedian());
+ mf.addNum(4);
+ mf.print();
+ System.out.println("Output: " + mf.findMedian());
+
+ }
+
+}

Hard/FindMedianFromDataStream/MedianFinder.java

@@ -0,0 +1,44 @@
+package Hard.FindMedianFromDataStream;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Solution
+ */
+public class MedianFinder {
+
+ private List<Integer> nums;
+
+ /** initialize your data structure here. */
+ public MedianFinder() {
+ this.nums = new ArrayList<Integer>();
+ }
+ 
+ public void addNum(int num) {
+ for (int i = 0; i < nums.size(); i++) {
+ if (nums.get(i) >= num) {
+ nums.add(i, num);
+ return;
+ }
+ }
+ nums.add(num);
+ }
+ 
+ public double findMedian() {
+ if (this.nums.size() == 0) {
+ return -1;
+ }
+ if (this.nums.size() % 2 != 0) {
+ // odd
+ return this.nums.get((this.nums.size()-1)/2);
+ } else {
+ // even
+ return (this.nums.get((this.nums.size()-1)/2) + this.nums.get(this.nums.size()/2)) / 2.0;
+ }
+ }
+ 
+ public void print() {
+ System.out.println(this.nums.toString());
+ }
+}

Hard/FindMedianFromDataStream/README.md

@@ -0,0 +1,27 @@
+
+# Find Median from Data Stream
+[Leetcode Link](https://leetcode.com/problems/find-median-from-data-stream/)
+
+## Problem:
+
+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
+```

README.md

@@ -78,6 +78,7 @@ Languages used: Java and Python
  - [Longest Consecutive Sequence](Hard/LongestConsecutiveSequence)
  - [First Missing Positive](Hard/FirstMissingPositive)
  - [Insert Interval](Hard/InsertInterval)
+ - [Find Median From Data Stream](Hard/FindMedianFromDataStream)
 
 ---