Two strings are given and you have to modify 1st string such that all the common characters of the 2nd string have to be removed and the uncommon characters of the 2nd string have to be concatenated with uncommon characters of the 1st string.

Examples:

Input : S1 = "aacdb"
        S2 = "gafd"
Output : "cbgf"

Input : S1 = "abcs";
        S2 = "cxzca";
Output : "bsxz"

This problem has existing solution please refer Concatenated string with uncommon characters of two strings link. We can solve this problem quickly in Python using Set and List Comprehension. Approach is simple,

1. Convert both strings into set so that they could have only unique characters. Now take intersection of two sets to get common character both strings have.
2. Now separate out those characters in each string which are not common in both of them and concatenate the characters.

# Function to concatenated string with uncommon
# characters of two strings

def uncommonConcat(str1, str2):

	# convert both strings into set
	set1 = set(str1)
	set2 = set(str2)

	# take intersection of two sets to get list of
	# common characters
	common = list(set1 & set2)

	# separate out characters in each string
	# which are not common in both strings
	result = [ch for ch in str1 if ch not in common] + [ch for ch in str2 if ch not in common]

	# join each character without space to get
	# final string
	print( ''.join(result) )

# Driver program
if __name__ == "__main__":
	str1 = 'aacdb'
	str2 = 'gafd'
	uncommonConcat(str1,str2)

Output:

cbgf