Python Merge Sort
Python3 ExamplesMerge sort (or mergesort) is an efficient sorting algorithm based on the merge operation. This algorithm is a very typical application of the divide and conquer (Divide and Conquer) method.
Divide and Conquer:
- Divide: Recursively divide the current sequence into two halves equally.
- Integrate: Integrate the subsequences obtained in the previous step together (merge) while maintaining the order of elements.
Example
def merge(arr, l, m, r):
n1 = m - l + 1
n2 = r- m
# Create temporary arrays
L = [0] * (n1)
R = [0] * (n2)
# Copy data to temporary arrays L[] and R[]
for i in range(0 , n1):
L[i] = arr[l + i]
for j in range(0 , n2):
R[j] = arr[m + 1 + j]
# Merge the temporary arrays into arr[l..r]
i = 0 # Initialize the index of the first subarray
j = 0 # Initialize the index of the second subarray
k = l # Initialize the index of the merged subarray
while i < n1 and j < n2 :
if L[i] <= R[j]:
arr[k] = L[i]
i += 1
else:
arr[k] = R[j]
j += 1
k += 1
# Copy the remaining elements of L[]
while i < n1:
arr[k] = L[i]
i += 1
k += 1
# Copy the remaining elements of R[]
while j < n2:
arr[k] = R[j]
j += 1
k += 1
def mergeSort(arr,l,r):
if l < r:
m = int((l+(r-1))/2)
mergeSort(arr, l, m)
mergeSort(arr, m+1, r)
merge(arr, l, m, r)
arr = [12, 11, 13, 5, 6, 7]
n = len(arr)
print ("Given array")
for i in range(n):
print ("%d" %arr[i]),
mergeSort(arr,0,n-1)
print ("\n\nSorted array")
for i in range(n):
print ("%d" %arr[i]),
Executing the above code produces the following output:
给定的数组 12 11 13 5 6 7 排序后的数组 5 6 7 11 12 13Other Extensions