# LeetCode 884. Uncommon Words from Two Sentences

## Description

https://leetcode.com/problems/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"]
```

Note:

1. `0 <= A.length <= 200`
2. `0 <= B.length <= 200`
3. `A` and `B` both contain only spaces and lowercase letters.

## Explanation

Count A words and B words separately and find out those words only occur either in A or B once.

## Python Solution

``````class Solution:
def uncommonFromSentences(self, A: str, B: str) -> List[str]:
results = []

a_counter = {}

a_words = A.split()
for word in a_words:
a_counter[word] = a_counter.get(word, 0) + 1

b_counter = {}
b_words = B.split()
for word in b_words:
b_counter[word] = b_counter.get(word, 0) + 1

for key, value in a_counter.items():
if key not in b_counter and value == 1:
results.append(key)

for key, value in b_counter.items():
if key not in a_counter and value == 1:
results.append(key)

return results``````
• Time Complexity: O(N).
• Space Complexity: O(N).