A **sentence** is a string of single-space separated words where 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.

Given two **sentences** `s1` and `s2`, return _a list of all the **uncommon words**_. You may return the answer in **any order**.

**Example 1:**

**Input:** s1 = "this apple is sweet", s2 = "this apple is sour"
**Output:** \["sweet","sour"\]

**Example 2:**

**Input:** s1 = "apple apple", s2 = "banana"
**Output:** \["banana"\]

**Constraints:**

*   `1 <= s1.length, s2.length <= 200`
*   `s1` and `s2` consist of lowercase English letters and spaces.
*   `s1` and `s2` do not have leading or trailing spaces.
*   All the words in `s1` and `s2` are separated by a single space.


def k_similarity(s1, s2):
    k = 0
    a, b = list(s1), list(s2)
    for i in range(len(a)):
        if a[i] != b[i]:
            for j in range(i + 1, len(b)):
                if a[i] == b[j] and a[j] != b[j]:
                    a[i], a[j] = a[j], a[i]
                    k += 1
                    break
    return k
