Create merge sort

merge sort

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+# Python program for implementation of MergeSort
+
+# Merges two subarrays of arr[].
+# First subarray is arr[l..m]
+# Second subarray is arr[m+1..r]
+
+
+def merge(arr, l, m, r):
+	n1 = m - l + 1
+	n2 = r - m
+
+	# create temp arrays
+	L = [0] * (n1)
+	R = [0] * (n2)
+
+	# Copy data to temp 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 temp arrays back into arr[l..r]
+	i = 0	 # Initial index of first subarray
+	j = 0	 # Initial index of second subarray
+	k = l	 # Initial index of 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[], if there
+	# are any
+	while i < n1:
+		arr[k] = L[i]
+		i += 1
+		k += 1
+
+	# Copy the remaining elements of R[], if there
+	# are any
+	while j < n2:
+		arr[k] = R[j]
+		j += 1
+		k += 1
+
+# l is for left index and r is right index of the
+# sub-array of arr to be sorted
+
+
+def mergeSort(arr, l, r):
+	if l < r:
+
+		# Same as (l+r)//2, but avoids overflow for
+		# large l and h
+		m = l+(r-l)//2
+
+		# Sort first and second halves
+		mergeSort(arr, l, m)
+		mergeSort(arr, m+1, r)
+		merge(arr, l, m, r)
+
+
+# Driver code to test above
+arr = [12, 11, 13, 5, 6, 7]
+n = len(arr)
+print("Given array is")
+for i in range(n):
+	print("%d" % arr[i],end=" ")
+
+mergeSort(arr, 0, n-1)
+print("\n\nSorted array is")
+for i in range(n):
+	print("%d" % arr[i],end=" ")
+
+# This code is contributed by Mohit Kumra