From 578845a6b5491c797ddad8eb61297e9f6383962c Mon Sep 17 00:00:00 2001
From: Tony Sappe <tony@motiondsp.com>
Date: Fri, 29 Jul 2016 15:48:47 -0400
Subject: [PATCH] Improved MergeSort.py

* Added Python3 support
---
 BubbleSort.py    |  9 ++++-
 InsertionSort.py | 10 +++++-
 LinearSearch.py  | 12 +++++--
 MergeSort.py     | 91 ++++++++++++++++++++++++++++++------------------
 QuickSort.py     | 10 +++++-
 README.md        | 33 +++++++++++++++---
 6 files changed, 121 insertions(+), 44 deletions(-)

diff --git a/BubbleSort.py b/BubbleSort.py
index d74b5b223b9e..9f357961782b 100644
--- a/BubbleSort.py
+++ b/BubbleSort.py
@@ -1,3 +1,4 @@
+import sys
 
 
 def simple_bubble_sort(int_list):
@@ -13,9 +14,15 @@ def simple_bubble_sort(int_list):
 
 
 def main():
+    # Python 2's `raw_input` has been renamed to `input` in Python 3
+    if sys.version_info.major < 3:
+        input_function = raw_input
+    else:
+        input_function = input
+
     try:
         print("Enter numbers separated by spaces:")
-        s = raw_input()
+        s = input_function()
         inputs = list(map(int, s.split(' ')))
         if len(inputs) < 2:
             print('No Enough values to sort!')
diff --git a/InsertionSort.py b/InsertionSort.py
index 74cbc57e8306..a577c4a8119b 100644
--- a/InsertionSort.py
+++ b/InsertionSort.py
@@ -1,3 +1,5 @@
+import sys
+
 
 def simple_insertion_sort(int_list):
     count = len(int_list)
@@ -13,9 +15,15 @@ def simple_insertion_sort(int_list):
 
 
 def main():
+    # Python 2's `raw_input` has been renamed to `input` in Python 3
+    if sys.version_info.major < 3:
+        input_function = raw_input
+    else:
+        input_function = input
+
     try:
         print("Enter numbers separated by spaces:")
-        s = raw_input()
+        s = input_function()
         inputs = list(map(int, s.split(' ')))
         if len(inputs) < 2:
             print('No Enough values to sort!')
diff --git a/LinearSearch.py b/LinearSearch.py
index 61c9e0dd5691..82595ededf38 100644
--- a/LinearSearch.py
+++ b/LinearSearch.py
@@ -1,3 +1,5 @@
+import sys
+
 
 def sequential_search(alist, target):
     for index, item in enumerate(alist):
@@ -9,11 +11,17 @@ def sequential_search(alist, target):
 
 
 def main():
+    # Python 2's `raw_input` has been renamed to `input` in Python 3
+    if sys.version_info.major < 3:
+        input_function = raw_input
+    else:
+        input_function = input
+
     try:
         print("Enter numbers separated by spaces")
-        s = raw_input()
+        s = input_function()
         inputs = list(map(int, s.split(' ')))
-        target = int(raw_input('\nEnter a single number to be found in the list: '))
+        target = int(input_function('\nEnter a number to be found in list: '))
     except Exception as e:
         print(e)
     else:
diff --git a/MergeSort.py b/MergeSort.py
index 7ce144dc7a9f..ff3a31c701b0 100644
--- a/MergeSort.py
+++ b/MergeSort.py
@@ -1,36 +1,59 @@
-def mergeSort(alist):
-    print("Splitting ",alist)
-    if len(alist)>1:
-        mid = len(alist)//2
-        lefthalf = alist[:mid]
-        righthalf = alist[mid:]
-        mergeSort(lefthalf)
-        mergeSort(righthalf)
-        i=0
-        j=0
-        k=0
-        while i < len(lefthalf) and j < len(righthalf):
-            if lefthalf[i] < righthalf[j]:
-                alist[k]=lefthalf[i]
-                i=i+1
+import sys
+
+
+def merge_sort(alist):
+    print("Splitting ", alist)
+    if len(alist) > 1:
+        mid = len(alist) // 2
+        left_half = alist[:mid]
+        right_half = alist[mid:]
+        merge_sort(left_half)
+        merge_sort(right_half)
+        i = j = k = 0
+
+        while i < len(left_half) and j < len(right_half):
+            if left_half[i] < right_half[j]:
+                alist[k] = left_half[i]
+                i += 1
             else:
-                alist[k]=righthalf[j]
-                j=j+1
-            k=k+1
-
-        while i < len(lefthalf):
-            alist[k]=lefthalf[i]
-            i=i+1
-            k=k+1
-
-        while j < len(righthalf):
-            alist[k]=righthalf[j]
-            j=j+1
-            k=k+1
-    print("Merging ",alist)
-
-print("Enter numbers seprated by space")
-s = input()
-numbers = list(map(int, s.split()))
-mergeSort(numbers)
+                alist[k] = right_half[j]
+                j += 1
+            k += 1
+
+        while i < len(left_half):
+            alist[k] = left_half[i]
+            i += 1
+            k += 1
+
+        while j < len(right_half):
+            alist[k] = right_half[j]
+            j += 1
+            k += 1
+    print("Merging ", alist)
+    return alist
+
+
+def main():
+    # Python 2's `raw_input` has been renamed to `input` in Python 3
+    if sys.version_info.major < 3:
+        input_function = raw_input
+    else:
+        input_function = input
+
+    try:
+        print("Enter numbers separated by spaces:")
+        s = input_function()
+        inputs = list(map(int, s.split(' ')))
+        if len(inputs) < 2:
+            print('No Enough values to sort!')
+            raise Exception
+
+    except Exception as e:
+        print(e)
+    else:
+        sorted_input = merge_sort(inputs)
+        print('\nSorted list (min to max): {}'.format(sorted_input))
 
+if __name__ == '__main__':
+    print('==== Merge Sort ====\n')
+    main()
diff --git a/QuickSort.py b/QuickSort.py
index 7221cfe754bb..2d922a3de3b0 100644
--- a/QuickSort.py
+++ b/QuickSort.py
@@ -1,3 +1,5 @@
+import sys
+
 
 def quick_sort(A, p, r):
     if p < r:
@@ -18,9 +20,15 @@ def partition(A, p, r):
 
 
 def main():
+    # Python 2's `raw_input` has been renamed to `input` in Python 3
+    if sys.version_info.major < 3:
+        input_function = raw_input
+    else:
+        input_function = input
+
     try:
         print("Enter numbers separated by spaces")
-        s = raw_input()
+        s = input_function()
         inputs = list(map(int, s.split(' ')))
     except Exception as e:
         print(e)
diff --git a/README.md b/README.md
index b44e12e935af..65f0c70dad31 100644
--- a/README.md
+++ b/README.md
@@ -19,12 +19,9 @@ __Properties__
 * Best case performance	O(n)
 * Average case performance	O(n^2)
 
-
 ###### View the algorithm in [action][bubble-toptal]
 
 
-### Caesar
-Add comments here
 
 ### Insertion
 ![alt text][insertion-image]
@@ -36,10 +33,22 @@ __Properties__
 * Best case performance	O(n)
 * Average case performance	O(n^2)
 
-
 ###### View the algorithm in [action][insertion-toptal]
 
 
+## Merge
+![alt text][merge-image]
+
+From [Wikipedia][merge-wiki]: In computer science, merge sort (also commonly spelled mergesort) is an efficient, general-purpose, comparison-based sorting algorithm. Most implementations produce a stable sort, which means that the implementation preserves the input order of equal elements in the sorted output. Mergesort is a divide and conquer algorithm that was invented by John von Neumann in 1945.
+
+__Properties__
+* Worst case performance	O(n log n)
+* Best case performance	O(n)
+* Average case performance	O(n)
+
+
+###### View the algorithm in [action][merge-toptal]
+
 ## Quick
 ![alt text][quick-image]
 
@@ -50,9 +59,19 @@ __Properties__
 * Best case performance	O(n log n) or O(n) with three-way partition
 * Average case performance	O(n^2)
 
-
 ###### View the algorithm in [action][quick-toptal]
 
+
+## Search Algorithms
+
+### Linear
+Add comments here
+
+## Ciphers
+
+### Caesar
+Add comments here
+
 [bubble-toptal]: https://www.toptal.com/developers/sorting-algorithms/bubble-sort
 [bubble-wiki]: https://en.wikipedia.org/wiki/Bubble_sort
 [bubble-image]: https://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Bubblesort-edited-color.svg/220px-Bubblesort-edited-color.svg.png "Bubble Sort"
@@ -64,3 +83,7 @@ __Properties__
 [quick-toptal]: https://www.toptal.com/developers/sorting-algorithms/quick-sort
 [quick-wiki]: https://en.wikipedia.org/wiki/Quicksort
 [quick-image]: https://upload.wikimedia.org/wikipedia/commons/6/6a/Sorting_quicksort_anim.gif "Quick Sort"
+
+[merge-toptal]: https://www.toptal.com/developers/sorting-algorithms/merge-sort
+[merge-wiki]: https://en.wikipedia.org/wiki/Merge_sort
+[merge-image]: https://upload.wikimedia.org/wikipedia/commons/c/cc/Merge-sort-example-300px.gif "Merge Sort"