Finding the Length of the Last Word in a String

Identifying Problem Isomorphism

“Finding the Length of Last Word in a String” is approximately isomorphic to “Reverse Words in a String III”.

Reasoning:

Both problems involve performing operations on the words in a string. In “Length of Last Word in a String”, the task is to find the length of the last word. In “Reverse Words in a String III”, each word in the string must be reversed. The tasks are different but structurally similar, as both require splitting the string into words and then processing those words.

The problem “Last Word Length” is another similar problem.

Reasoning:

This problem directly asks for finding the length of the last word in a given string, which is exactly the same as the “Length of Last Word in a String” problem. It can serve as an isomorphic problem with a perfect mapping. However, if the problem names are the same, we will skip this option.

Please note that these are not exact mappings, but the problems are structurally similar, and the approaches to solve these problems are also similar.

Based on simplicity, the order is:

Length of Last Word in a String
Reverse Words in a String III

“Length of Last Word in a String” is simpler as it requires only counting the length of the last word. “Reverse Words in a String III” is more complex as it requires reversing each word in the string, which involves a more string manipulation.

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class Solution(object):
    def lengthOfLastWord(self, s):
        """
        :type s: str
        :rtype: int
        """
        wordlist = s.split()
        if wordlist:
            return len(wordlist[-1])
        return 0

Problem Classification

The problem falls into several categories:

String Manipulation: The problem requires operations on strings, including splitting and length calculation.
Array/List Manipulation: The problem involves converting the string into a list of words and extracting elements from this list.
Conditional Logic: The solution has to handle different scenarios based on the presence or absence of words in the string.

Therefore, this is about String Manipulation, Array/List Manipulation, and Conditional Logic in the context of Problem-Solving.

Language Agnostic Coding Drills

Understanding Problem Statement: This problem requires finding the length of the last word in a sentence. The input is a string that represents a sentence. The words are separated by a space character. The solution should return an integer representing the length of the last word. If the input string does not have any words, it should return 0.
String Splitting: The first step in the problem-solving approach is to split the string into a list of words. This can be done using the split method which splits a string into a list where each word is a list item. The split method splits at spaces when no parameter is provided.
Conditional Statements: After obtaining the list of words, we use a conditional statement to check if the list is empty or not. This is important to avoid out of index errors in the subsequent steps if the list is empty.
Accessing Elements in a List: If the list is not empty, we access the last element of the list. In many languages, the index of -1 is used to access the last element in the list.
String Length Calculation: After accessing the last word in the list, we calculate the length of this word using the length function. This function generally takes a string as input and returns the number of characters in the string.
Return Statement: Finally, we return the calculated length. If the input string did not contain any words, we return 0 as specified in the problem statement.

In terms of increasing difficulty:

String operations (like splitting)
List operations (accessing elements)
Conditional statements (if condition)
Return statements (returning a result)
Combining all these to solve the problem.

Targeted Drills in Python

Drill 1: String operations - Splitting a string

The first drill would be to learn how to split a string into a list of words.

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sentence = "Hello World"
words = sentence.split()
print(words)  # Output: ['Hello', 'World']

Drill 2: List operations - Accessing elements

The next step would be to learn how to access elements in a list, especially the last element.

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words = ['Hello', 'World']
last_word = words[-1]
print(last_word)  # Output: 'World'

Drill 3: Conditional statements

Learn how to use conditional statements to check for certain conditions. In this case, check if a list is empty.

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words = ['Hello', 'World']

if words:
    print("List is not empty")
else:
    print("List is empty")

Drill 4: String Length Calculation

Get the length of a string using the len() function.

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word = "World"
length = len(word)
print(length)  # Output: 5

Drill 5: Return Statements

Learn to use the return statement in a function.

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def return_length(word):
    return len(word)

print(return_length("World"))  # Output: 5

Integrated Drill: Combining all drills

Now, combine all these concepts to solve the problem:

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def length_of_last_word(s):
    word_list = s.split()
    if word_list:
        return len(word_list[-1])
    return 0

print(length_of_last_word("Hello World"))  # Output: 5
print(length_of_last_word(""))  # Output: 0