"""

Keyboard Row Filter

Given a list of words, return the words that can be typed using letters from

only one row of an American QWERTY keyboard.

Reference: https://leetcode.com/problems/keyboard-row/description/

Complexity:

Time: O(n * m) where n is the number of words and m is average word length

Space: O(n)

"""

from __future__ import annotations

_KEYBOARD_ROWS: list[set[str]] = [

set("qwertyuiop"),

set("asdfghjkl"),

set("zxcvbnm"),

]

def find_keyboard_row(words: list[str]) -> list[str]:

"""Return words that can be typed using one keyboard row.

Args:

words: A list of words to check.

Returns:

A list of words each typable on a single keyboard row.

Examples:

>>> find_keyboard_row(["Hello", "Alaska", "Dad", "Peace"])

['Alaska', 'Dad']

"""

result: list[str] = []

for word in words:

for row in _KEYBOARD_ROWS:

if set(word.lower()).issubset(row):

result.append(word)

return result