Rewrite from Python to C++ please for this greedy algorithm using a file named act.txt as an input file. Thank you!

# merge algorithm
	def merge(l,r):
	# empty array to be used to hold sorted values
	s = []
	# append to s array until either l or r array is empty
	while len(l) != 0 and len(r) != 0:
	if l[0][1] > r[0][1]:
	s.append(l[0])
	l.remove(l[0])
	else:
	s.append(r[0])
	r.remove(r[0])
	# add the remaining value to the s array
	if len(l) == 0:
	s += r
	else:
	s += l
	return s
	# mergesort algorithm
	def mergesort(a):
	# if the array has only one element, return it
	if len(a) == 1:
	return a
	else:
	# call mergesort on half of the current input array
	mid = len(a)/2
	l = mergesort(a[:mid])
	r = mergesort(a[mid:])
	return merge(l,r)
	# selects non conflicting activites from a list
	def select_acts(a):
	n = len(a)
	sa = [a[0]]
	k = 0
	for m in range(1,n):
	if a[m][2] <= sa[k][1]:
	sa.append(a[m])
	k += 1
	return sa
	# opens the act file for reading
	input_file = open('act.txt','r')
	set_count = 0
	# loops until the end of the act file is reached
	while True:
	# gets a line from the file
	line = input_file.readline()
	# removes any spaces at the beginning or end of the line
	line = line.strip()
	# turn the line into a list
	line = line.split(' ')
	# if the end of file is reached, break
	if line == ['']:
	break
	# turn the list of strings into a list of integers
	line = map(int,line)
	if len(line) == 1:
	set_count += 1
	counter = line[0]
	acts = []
	# loop for the number of activities in the set
	for i in range(0,counter):
	line = input_file.readline()
	line = line.strip()
	line = line.split(' ')
	line = map(int,line)
	# create list of activities
	act = [line[0],line[1],line[2]]
	# put in list, to create a list of lists
	acts.append(act)
	# sort the list of lists
	sorted_acts = mergesort(acts)
	# select all activities that dont conflict
	selected_acts = select_acts(sorted_acts)
	# print results
	print "Set", set_count
	print "Number of activities selected =", len(selected_acts)
	g = "Activities:"
	for i in reversed(range(0,len(selected_acts))):
	g = g + " " + str(selected_acts[i][0])
	print g
	print " "
	input_file.close()