Keyboard Row

The problem is asking to return the words that can be typed using only one row of an American keyboard. To solve this problem, we can follow these steps:

  1. Define the Rows: Create sets for each row of the keyboard to represent the characters that can be typed using that row.
  2. Check Each Word: For each word in the given list, check if all the characters in the word are present in any one of the defined row sets.
  3. Append to Result: If all the characters are found in one row set, append the word to the result list.
  4. Return the Result: Return the list of words that meet the criteria.
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class Solution:
    def findWords(self, words: List[str]) -> List[str]:
        # Defining the keyboard rows
        row1 = set("qwertyuiop")
        row2 = set("asdfghjkl")
        row3 = set("zxcvbnm")

        result = []

        # Check each word
        for word in words:
            word_set = set(word.lower()) # Converting to lowercase to handle both cases
            if word_set.issubset(row1) or word_set.issubset(row2) or word_set.issubset(row3):
                result.append(word)

        return result

This code first constructs sets for each row of the keyboard and then iterates through each word to see if it is a subset of any one of these row sets. If it is, the word is added to the result list, and the final list is returned.

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class Solution:
    def findWords(self, words: List[str]) -> List[str]:
        row1 = set('qwertyuiop')
        row2 = set('asdfghjkl')
        row3 = set('zxcvbnm')

        res = []
        for word in words:
            w = set(word.lower())

            # Check if the word belongs to one of the rows
            if w.issubset(row1) or w.issubset(row2) or w.issubset(row3):
                res.append(word)

        return res

Identifying Problem Isomorphism

“Keyboard Row” has an approximate isomorphic problem “Find Words That Can Be Formed by Characters”.

In “Keyboard Row”, you are given a list of words and you need to return the words that can be typed using letters of alphabet that are on the same row of a keyboard.

Similarly, in “Find Words That Can Be Formed by Characters”, you are given an array of strings words and a string chars. A string B is a subset of string A if every letter B occurs in A including multiplicity. You need to return an array of all the strings in words that are subsets of the string chars.

The core concept in both problems revolves around checking if a condition holds for every character in a word. In “Keyboard Row”, we check if all characters of a word belong to the same row on a keyboard. In “Find Words That Can Be Formed by Characters”, we verify if all characters of a word are present in another string.

The complexity of the “Find Words That Can Be Formed by Characters” problem is higher because it not only checks for the existence of characters, but also considers the multiplicity of characters. Conversely, the “Keyboard Row” problem is simpler as it only requires checking if a character belongs to a specific row on a keyboard.

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class Solution:
    def findWords(self, words: List[str]) -> List[str]:
        set1 = {'q','w','e','r','t','y','u','i','o','p'}
        set2 = {'a','s','d','f','g','h','j','k','l'}
        set3 = {'z','x','c','v','b','n','m'}

        res = []
        for i in words:
            wordset = set(i.lower())
            if (wordset&set1 == wordset) or (wordset&set2 == wordset) or (wordset&set3 == wordset):
                res.append(i)
        return res

Problem Classification

This problem falls under the domain of array/string manipulation and filtering.

‘What’ Components:

  1. An array of strings named words is given.
  2. American keyboard has three rows of characters.
  3. We need to find and return the words from the words array that can be typed using the letters in only one row of the keyboard.

This problem is a type of filter operation, where we have a certain condition (in this case, whether the word can be formed by the characters in a single row of the keyboard), and we need to filter out the elements (words) that satisfy this condition.

The problem involves iterating through the given list of words and checking each word to see if it can be formed using the characters in a single row of the keyboard. If a word meets this condition, it should be included in the returned list. This problem is a straightforward application of string manipulation and filtering techniques.

Language Agnostic Coding Drills

  1. Dissect the code and identify each distinct concept:

a. Set Definition: This is where we define the keys of each row of the keyboard as separate sets. This is a basic concept of data structure understanding, specifically the set type.

b. Looping over a list: This is a fundamental concept where we iterate over a list of elements, in this case, the words list.

c. Converting strings to sets: We convert each word to a set of unique, lowercase characters. This concept involves understanding of sets and string manipulation.

d. Set Operations: This is where we use the set intersection operation (&) to check if the word can be constructed from characters of a single row. This requires understanding set operations.

e. Conditional Statements: This concept involves using if conditions to check whether a word belongs to any of the sets corresponding to keyboard rows.

f. List Manipulation: Appending to a list. When a word meets the required condition, it is added to the result list.

  1. List the concepts in order of increasing difficulty:

a. Set Definition: Basic understanding of data structures.

b. Looping over a list: Basic iteration concept.

c. List Manipulation: Basic concept of modifying list.

d. Converting strings to sets: Intermediate concept combining string manipulation and set understanding.

e. Conditional Statements: Intermediate concept, requires logical thinking.

f. Set Operations: More advanced understanding of set operations.

  1. Problem-solving approach leading to final solution:

a. Define the rows of the keyboard as separate sets. This will allow us to use efficient set operations to check if a word can be constructed from a single row.

b. Loop over the provided list of words. For each word, we need to perform some checks to decide whether it should be included in the result.

c. Convert each word to a set of unique, lowercase characters. This set represents all the distinct characters used in the word.

d. Use set operations to check whether the set of characters in the word is a subset of any of the sets representing keyboard rows. This is the condition for whether a word can be constructed from a single row.

e. If the word meets the condition, append it to the result list.

f. Once all words have been checked, return the result list. The result list should include all words that can be constructed using the characters in a single row of the keyboard.

Targeted Drills in Python

  1. Python Drills:

    a. Set Definition: Create a set with specific elements.

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    s = {'a', 'b', 'c'}
print(s)

    b. Looping over a list: Iterate over each element of a list.

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    l = ['a', 'b', 'c']
for i in l:
    print(i)

    c. List Manipulation: Append an element to a list.

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    l = ['a', 'b', 'c']
l.append('d')
print(l)

    d. Converting strings to sets: Convert a string to a set of characters.

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    s = "abc"
set_s = set(s)
print(set_s)

    e. Conditional Statements: Use if conditions to execute specific blocks of code.

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    x = 10
if x > 5:
    print("x is greater than 5")

    f. Set Operations: Use the set intersection operation.

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    s1 = {'a', 'b', 'c'}
s2 = {'b', 'c', 'd'}
print(s1 & s2)

  2. Problem-specific drills:

    a. Set Intersection Equality: Check if the intersection of two sets is equal to one of the sets.

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    s1 = {'a', 'b'}
s2 = {'a', 'b', 'c'}
print(s1 & s2 == s1)

    This drill is essential for our problem as it forms the basis of our condition to check if a word can be formed using characters from a single row of the keyboard.

  3. Integrating the drills:

    Start by defining the sets representing the rows of the keyboard. Then, initialize an empty result list.

    For each word in the input list, convert it to a set of unique, lowercase characters. If this set is equal to its intersection with any of the keyboard row sets, append the original word to the result list.

    After checking all words, return the result list.