sort methods

实现了常见的排序方法

BubbleSort.py

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+# Python 实现冒泡排序
+def bubbleSort(alist):
+    for passnum in range(len(alist)-1, 0, -1):
+        for i in range(passnum):
+            if alist[i] > alist[i+1]:
+                alist[i], alist[i+1] = alist[i+1], alist[i]
+    return alist
+
+alist = [54,26,93,17,77,31,44,55,20]
+print(bubbleSort(alist))
+
+# 改进的冒泡排序, 加入一个校验, 如果某次循环发现没有发生数值交换, 直接跳出循环
+def modiBubbleSort(alist):
+    exchange = True
+    passnum = len(alist) - 1
+    while passnum >= 1 and exchange:
+        exchange = False
+        for i in range(passnum):
+            if alist[i] > alist[i+1]:
+                alist[i], alist[i+1] = alist[i+1], alist[i]
+                exchange = True
+        passnum -= 1
+    return alist
+
+print(bubbleSort(alist))

InsertionSort.py

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+def insertionSort(alist):
+    for key, item in enumerate(alist):
+        index = key
+        while index > 0 and alist[index-1] > item:
+            alist[index] = alist[index-1]
+            index -= 1
+        alist[index] = item
+    return alist
+
+alist = [54,26,93,17,77,31,44,55,20]
+print(insertionSort(alist))
+
+def insertionSort2(alist):
+    for index in range(1, len(alist)):
+        currentvalue = alist[index]
+        position = index
+
+        while position > 0 and alist[index-1] > currentvalue:
+            alist[index] = alist[index-1]
+            position -= 1
+        alist[position] = currentvalue
+
+    return alist
+
+print(insertionSort2(alist))

MergeSort.py

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+def mergeSort(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 += 1
+            else:
+                alist[k] = righthalf[j]
+                j += 1
+            k += 1
+
+        while i < len(lefthalf):
+            alist[k] = lefthalf[i]
+            i += 1
+            k += 1
+        while j < len(righthalf):
+            alist[k] = righthalf[j]
+            j += 1
+            k += 1
+
+alist = [54,26,93,17,77,31,44,55,20]
+mergeSort(alist)
+print(alist)

QuickSort.py

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+def quickSort(alist):
+    quickSortHelper(alist, 0, len(alist)-1)
+
+def quickSortHelper(alist, first, last):
+    if first < last:
+        splitPoint = partition(alist, first, last)
+
+        quickSortHelper(alist, first, splitPoint-1)
+        quickSortHelper(alist, splitPoint+1, last)
+
+def partition(alist, first, last):
+    pivotvlue = alist[first]
+
+    leftmark = first+1
+    rightmark = last
+    done = False
+
+    while not done:
+        while alist[leftmark] <= pivotvlue and leftmark <= rightmark:
+            leftmark += 1
+        while alist[rightmark] >= pivotvlue and rightmark >= leftmark:
+            rightmark -= 1
+
+        if leftmark > rightmark:
+            done = True
+        else:
+            alist[leftmark], alist[rightmark] = alist[rightmark], alist[leftmark]
+    alist[rightmark], alist[first] = alist[first], alist[rightmark]
+    return rightmark
+
+alist = [54,26,93,17,77,31,44,55,20]
+quickSort(alist)
+print(alist)

SelectionSort.py

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+# 选择排序, 纯粹练手 - -||
+def selectionSort(alist):
+    for i in range(len(alist)-1):
+        min = i
+        for j in range(i+1, len(alist)):
+            if alist[j] < alist[min]:
+                min = j
+        alist[i], alist[min] = alist[min], alist[i]
+    return alist
+
+alist = [54,26,93,17,77,31,44,55,20]
+print(selectionSort(alist))

ShellSort.py

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+# python实现希尔排序
+def shellSort(alist):
+    sublistcount= len(alist)//2
+    while sublistcount > 0:
+        for startposition in range(sublistcount):
+            gapInsertionSort(alist, startposition, sublistcount)
+        sublistcount = sublistcount//2
+    return alist
+
+def gapInsertionSort(alist, start, gap):
+    for i in range(start+gap, len(alist), gap):
+        currentValue = alist[i]
+        position = i
+
+        while position >= gap and alist[position-gap] > currentValue:
+            alist[position] = alist[position-gap]
+            position = position-gap
+        alist[position] = currentValue
+
+alist = [54,26,93,17,77,31,44,55,20]
+print(shellSort(alist))

Target Offer/README.md

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+# Python实现剑指offer
+剑指offer一书的python实现。