# Challenge name: Uncommon words from two sentences
#
# We are given two sentences A and B.
# (A sentence is a string of space separated words.
# Each word consists only of lowercase letters.)
#
# A word is uncommon if it appears exactly once in one of the sentences,
# and does not appear in the other sentence.
#
# Return a list of all uncommon words.
# You may return the list in any order.
#
# Example 1:
# Input: A = "this apple is sweet", B = "this apple is sour"
# Output: ["sweet","sour"]
#
# Example 2:
# Input: A = "apple apple", B = "banana"
# Output: ["banana"]