choire: find median

Author: rupeshtiwari

README.md

@@ -34,6 +34,8 @@
     - [DFS Vs BFS](#dfs-vs-bfs)
 - [Sorting](#sorting)
   - [Merge Sort](#merge-sort)
+    - [Implement Merge Sort](#implement-merge-sort)
+    - [Find Median Values](#find-median-values)
 - [Math.floor](#mathfloor)
 - [Math.round](#mathround)
 
@@ -348,7 +350,19 @@ Example: Suppose you have given a tree structure and asked to calculate the aver
 
 Browser's JavaScript Engine (`Array.prototype.sort`) uses merge sort maximum time. Runtime complexity O(n logn), Memory complexity O(n) because we have to create new list. It uses divide-and-conquer algorithm! and also it is recursive.
 
-[Exercise File](src/sorting/merge-sort.mjs)
+#### Implement Merge Sort
+
+[Exercise File](src/sorting/merge-sort/merge-sort.mjs)
+
+#### Find Median Values
+
+2 sorted arrays find the median element. Median is the middle index its not an average of values in an sorted array.
+
+![](https://i.imgur.com/anPm3Yx.png)
+
+So in order to find median we can use the stich algorithm since arrays are already sorted. Then we can find the middle index.
+
+[Exercise File](src/sorting/merge-sort/find-median-values.mjs)
 
 ## Math.floor
 

src/sorting/merge-sort/find-median-values.mjs

@@ -0,0 +1,61 @@
+/**
+ * 2 sorted arrays find the median element
+ * It is the middle index its not an average
+ * [1,5,8,9]
+ * [2,3,7,10]
+ *
+ */
+
+function stitch(left = [], right = []) {
+  const results = [];
+  while (left.length && right.length) {
+    if (left[0] < right[0]) {
+      results.push(left.shift());
+    } else {
+      results.push(right.shift());
+    }
+  }
+
+  return [...results, ...left, ...right];
+}
+
+function findMedian(left, right) {
+  const result = stitch(left, right);
+  return Math.floor(result.length / 2);
+}
+assert(
+  [
+    [1, 5, 8, 9],
+    [2, 3, 7, 10],
+  ],
+  findMedian([1, 5, 8, 9], [2, 3, 7, 10]),
+  4
+);
+assert(
+  [
+    [1, 5, 8, 9],
+    [2, 3, 7, 10],
+  ],
+  stitch([1, 5, 8, 9], [2, 3, 7, 10]).toString(),
+  [1, 2, 3, 5, 7, 8, 9, 10].toString()
+);
+
+function assert(given, result, expected) {
+  if (result === expected) {
+    console.log('PASS');
+  } else {
+    console.log('FAIL');
+  }
+
+  console.log(
+    'Given: [' +
+      given +
+      ']' +
+      'Result: [' +
+      result +
+      ']' +
+      'Expected: [' +
+      expected +
+      ']'
+  );
+}