From ed760f9ac149d9f2a297a51831939e944d5cc108 Mon Sep 17 00:00:00 2001
From: danielyan86 <516495459@qq.com>
Date: Wed, 12 Dec 2018 16:04:22 +0800
Subject: [PATCH] =?UTF-8?q?1=20=E4=BC=98=E5=8C=96=E4=BB=A3=E7=A0=81?=
 =?UTF-8?q?=EF=BC=8C=E6=A0=B9=E6=8D=AEPEP8=E6=A0=BC=E5=BC=8F=E5=8C=96?=
 =?UTF-8?q?=E4=BB=A3=E7=A0=81?=
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---
 python/12_sorts/merge_sort.py | 37 +++++++++++++++++++++++++---------
 python/12_sorts/quick_sort.py | 38 ++++++++++++++++++++++++++---------
 2 files changed, 55 insertions(+), 20 deletions(-)

diff --git a/python/12_sorts/merge_sort.py b/python/12_sorts/merge_sort.py
index 9bcacecf..f1c5e71a 100644
--- a/python/12_sorts/merge_sort.py
+++ b/python/12_sorts/merge_sort.py
@@ -4,21 +4,23 @@
 
 from typing import List
 
+
 def merge_sort(a: List[int]):
-    _merge_sort_between(a, 0, len(a)-1)
+    _merge_sort_between(a, 0, len(a) - 1)
+
 
 def _merge_sort_between(a: List[int], low: int, high: int):
     # The indices are inclusive for both low and high.
-    if low >= high: return
-    mid = low + (high - low)//2
-    _merge_sort_between(a, low, mid)
-    _merge_sort_between(a, mid+1, high)
+    if low < high:
+        mid = low + (high - low) // 2
+        _merge_sort_between(a, low, mid)
+        _merge_sort_between(a, mid + 1, high)
+        _merge(a, low, mid, high)
 
-    _merge(a, low, mid, high)
 
 def _merge(a: List[int], low: int, mid: int, high: int):
     # a[low:mid], a[mid+1, high] are sorted.
-    i, j = low, mid+1
+    i, j = low, mid + 1
     tmp = []
     while i <= mid and j <= high:
         if a[i] <= a[j]:
@@ -29,8 +31,23 @@ def _merge(a: List[int], low: int, mid: int, high: int):
             j += 1
     start = i if i <= mid else j
     end = mid if i <= mid else high
-    tmp.extend(a[start:end+1])
-    a[low:high+1] = tmp
+    tmp.extend(a[start:end + 1])
+    a[low:high + 1] = tmp
+
+
+def test_merge_sort():
+    a1 = [3, 5, 6, 7, 8]
+    merge_sort(a1)
+    assert a1 == [3, 5, 6, 7, 8]
+    a2 = [2, 2, 2, 2]
+    merge_sort(a2)
+    assert a2 == [2, 2, 2, 2]
+    a3 = [4, 3, 2, 1]
+    merge_sort(a3)
+    assert a3 == [1, 2, 3, 4]
+    a4 = [5, -1, 9, 3, 7, 8, 3, -2, 9]
+    merge_sort(a4)
+    assert a4 == [-2, -1, 3, 3, 5, 7, 8, 9, 9]
 
 
 if __name__ == "__main__":
@@ -45,4 +62,4 @@ def _merge(a: List[int], low: int, mid: int, high: int):
     merge_sort(a3)
     print(a3)
     merge_sort(a4)
-    print(a4)
\ No newline at end of file
+    print(a4)
diff --git a/python/12_sorts/quick_sort.py b/python/12_sorts/quick_sort.py
index f4267512..b4f923cf 100644
--- a/python/12_sorts/quick_sort.py
+++ b/python/12_sorts/quick_sort.py
@@ -5,22 +5,25 @@
 from typing import List
 import random
 
+
 def quick_sort(a: List[int]):
-    _quick_sort_between(a, 0, len(a)-1)
+    _quick_sort_between(a, 0, len(a) - 1)
+
 
 def _quick_sort_between(a: List[int], low: int, high: int):
-    if low >= high: return
-    # get a random position as the pivot
-    k = random.randint(low, high)
-    a[low], a[k] = a[k], a[low]
+    if low < high:
+        # get a random position as the pivot
+        k = random.randint(low, high)
+        a[low], a[k] = a[k], a[low]
+
+        m = _partition(a, low, high)  # a[m] is in final position
+        _quick_sort_between(a, low, m - 1)
+        _quick_sort_between(a, m + 1, high)
 
-    m = _partition(a, low, high)   # a[m] is in final position
-    _quick_sort_between(a, low, m-1)
-    _quick_sort_between(a, m+1, high)
 
 def _partition(a: List[int], low: int, high: int):
     pivot, j = a[low], low
-    for i in range(low+1, high+1):
+    for i in range(low + 1, high + 1):
         if a[i] <= pivot:
             j += 1
             a[j], a[i] = a[i], a[j]  # swap
@@ -28,6 +31,21 @@ def _partition(a: List[int], low: int, high: int):
     return j
 
 
+def test_quick_sort():
+    a1 = [3, 5, 6, 7, 8]
+    quick_sort(a1)
+    assert a1 == [3, 5, 6, 7, 8]
+    a2 = [2, 2, 2, 2]
+    quick_sort(a2)
+    assert a2 == [2, 2, 2, 2]
+    a3 = [4, 3, 2, 1]
+    quick_sort(a3)
+    assert a3 == [1, 2, 3, 4]
+    a4 = [5, -1, 9, 3, 7, 8, 3, -2, 9]
+    quick_sort(a4)
+    assert a4 == [-2, -1, 3, 3, 5, 7, 8, 9, 9]
+
+
 if __name__ == "__main__":
     a1 = [3, 5, 6, 7, 8]
     a2 = [2, 2, 2, 2]
@@ -40,4 +58,4 @@ def _partition(a: List[int], low: int, high: int):
     quick_sort(a3)
     print(a3)
     quick_sort(a4)
-    print(a4)
\ No newline at end of file
+    print(a4)