def LinearSelect(arr, start_idx, end_idx, k):
n = end_idx - start_idx + 1
'''
算法时间复杂度接近o(1)
'''
if n < 20:
sort.QuickSort(arr, start_idx, end_idx)
return arr[k - 1]
'''
每组5个元素进行排序，排序时间复杂度相当于O(1)
并将每组的中味数放在数组的前边，进行排序，然后选取中位数
'''
for i in range(0, n / 5):
sort.QuickSort(arr, i * 5, i * 5 + 4)
arr[i], arr[i * 5 + 2] = Swap(arr[i], arr[i * 5 + 2])
'''
选取中位数，不需要这么写，递归的调用本方法即可
sort.QuickSort(arr, 0, n/5)
m = arr[2]
'''
m = LinearSelect(arr, 0, n / 5, n / 10)
'''
分割三部分
'''
small_n, equal_n = Partition(arr, m, 0, n - 1)
if small_n > k:
return LinearSelect(arr, 0, small_n - 1, k)
elif small_n + equal_n < k:
return LinearSelect(arr, small_n + equal_n, n - small_n - equal_n - 1,
k - small_n - equal_n)
else:
return arr[k - 1]
else:
k += 1
'''
k超越j，说明已经分配完毕
'''
if k > j:
return i, j - i + 1
while i < j and arr[j] > m:
j -= 1
if i < j:
arr[i], arr[j] = Swap(arr[i], arr[j])
'''
如果和m相同，那么需要后移
'''
if arr[i] < m:
i += 1
j -= 1
if __name__ == '__main__':
print('start...')
arr = [156, 81, 127, 147, 43, 196, 46, 38, 181]
k = len(arr) / 2
m = LinearSelect(arr, 0, len(arr) - 1, k)
print m
sort.QuickSort(arr, 0, len(arr) - 1)
print arr[k - 1]
testList.append(randomNum)
sort.IterativeMergeSort(testList)
end = time.time_ns()
runTime = (end - start) / 1000000
print("Run Time: {} ms.".format(runTime))
print()
print()
# Quick Sort
print("Quick Sort")
testList.clear()
start = time.time_ns()
for i in range(LIST_SIZE):
randomNum = random.randint(0, LIST_SIZE * 10)
testList.append(randomNum)
sort.QuickSort(testList)
end = time.time_ns()
runTime = (end - start) / 1000000
print("Run Time: {} ms.".format(runTime))
testList.clear()
start = time.time_ns()
for i in range(LIST_SIZE * 10):
randomNum = random.randint(0, LIST_SIZE * 10)
testList.append(randomNum)
sort.QuickSort(testList)
end = time.time_ns()
runTime = (end - start) / 1000000
print("Run Time: {} ms.".format(runTime))
testList.clear()
print(inList)
elif sortName[0:3] == 'In':
print(inList)
sort.InsertionSort(inList)
print(inList)
elif sortName[0] == 'M':
print(inList)
sort.MergeSort(inList)
print(inList)
elif sortName[0] == 'I':
print(inList)
sort.IterativeMergeSort(inList)
print(inList)
elif sortName[0] == 'Q':
print(inList)
sort.QuickSort(inList)
print(inList)
elif sortName[0] == 'S':
print(inList)
sort.ShellSort(inList)
print(inList)
elif output[0] == 'N':
if sortName[0] == 'B':
sort.BubbleSort(inList)
elif sortName[0:3] == 'In':
sort.InsertionSort(inList)
elif sortName[0] == 'M':
sort.MergeSort(inList)
elif sortName[0] == 'I':
sort.IterativeMergeSort(inList)
elif sortName[0] == 'Q':
def init(item):
quicksort = sort.QuickSort(item)
return quicksort
numberOfInt = sys.argv[2]
mylist = []
for i in range(int(numberOfInt)):
randNumber = random.randint(1, int(numberOfInt))
mylist.append(randNumber)
if len(sys.argv) == 4:
printString = sys.argv[3]
if printString == 'PRINT':
print("List before sorting:\n", mylist)
else:
print('you can only input PRINT as the last argument')
if sortType == 'BubbleSort':
mySort = sort.BubbleSort(mylist)
elif sortType == 'InsertionSort':
mySort = sort.InsertionSort(mylist)
elif sortType == 'MergeSort':
mySort = sort.MergeSort(mylist)
elif sortType == 'IterativeMergeSort':
mySort = sort.IterativeMergeSort(mylist)
elif sortType == 'QuickSort':
mySort = sort.QuickSort(mylist, 0, len(mylist) - 1)
elif sortType == 'ShellSort':
mySort = sort.ShellSort(mylist)
if len(sys.argv) == 4:
if printString == 'PRINT' and sortType == 'BubbleSort' or sortType == 'InsertionSort' or sortType == 'MergeSort' or sortType == 'IterativeMergeSort' or sortType == 'QuickSort' or sortType == 'ShellSort':
print("List after sorting:\n ", mylist)
else:
print("You need to input sort type correctly!")