Detect Capital

The problem involves checking the usage of capital letters in a given word. This checking process adheres to a few defined rules as described. The solution should return True if the word meets these rules, and False otherwise.

The Python solution involves defining a function detectCapitalUse within a Solution class that accepts a string parameter word.

Here’s the solution:

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class Solution:
    def detectCapitalUse(self, word: str) -> bool:
        # Check if all letters are uppercase
        if word.isupper():
            return True
        # Check if all letters are lowercase
        elif word.islower():
            return True
        # Check if only the first letter is uppercase
        elif word[0].isupper() and word[1:].islower():
            return True
        # If none of the conditions are met, return False
        else:
            return False

In the code above, the built-in Python string methods are used:

isupper(): Checks if all the characters are in uppercase.
islower(): Checks if all the characters are in lowercase.

In the third condition, the first character of the string word[0] is checked if it’s uppercase and the rest of the string word[1:] is checked if it’s lowercase.

If any of these conditions is met, the function returns True, else False. This covers all the conditions specified in the problem.

10 Prerequisite LeetCode Problems

“Detect Capital” involves string manipulation and character property analysis in a string. Here are 10 problems to prepare:

344. Reverse String: Helps in understanding basic string manipulation.
709. To Lower Case: A problem to understand conversion of character case.
520. Detect Capital: A problem similar to the target but simpler.
125. Valid Palindrome: This problem involves string manipulation and character analysis.
383. Ransom Note: Helps in understanding string comparison and character frequency count.
387. First Unique Character in a String: Gives understanding about how to scan and analyze characters in a string.
242. Valid Anagram: Anagram detection will give you more experience with character property analysis.
290. Word Pattern: This problem involves mapping and comparison of strings which will help in understanding string manipulation.
205. Isomorphic Strings: Understanding of string mapping and comparison.
293. Flip Game: This problem helps with understanding the manipulation and comparison of strings.

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class Solution:
    def detectCapitalUse(self, word: str) -> bool:
        count = 0
        if len(word) == 1:
            return True

        for i in range(len(word)):
            if word[i].isupper():
                count += 1

        if count == 1 and word[0].isupper():
            return True
        if count == 0 or count == len(word):
            return True
        else:
            return False

Problem Classification

The problem belongs to the ‘String Processing’ and ‘Rule Checking’ domains of Computer Science.

‘What’ Components:

An input string called ‘word’.
Rules to determine if the usage of capitals in the string is ‘right’:
- All letters are capital.
- No letters are capital.
- Only the first letter is capital.
An output that is a boolean indicating if the usage of capitals in the input string is ‘right’.

This problem can be classified as a ‘Rule-Based Decision’ problem. We have a well-defined input (a string) and a set of rules which the string must abide by. The task is to determine whether the input adheres to these rules or not. The output is a binary decision, which makes this a classification problem. This problem also involves elements of string manipulation, as we have to examine and analyze the characters in the input string.

Identifying Problem Isomorphism

The problem “Detect Capital” can be mapped to “Check If Word Is Valid After Substitutions”.

The “Detect Capital” problem requires us to identify whether a word fits one of three distinct patterns (all uppercase, all lowercase, or only the first letter uppercase). Similarly, “Check If Word Is Valid After Substitutions” involves recognizing specific patterns in a string: checking if the string “abc” can be repeatedly substituted to eventually form a given word.

However, these problems are not exactly isomorphic as the operations required to solve them differ. “Detect Capital” primarily involves string property checks, while “Check If Word Is Valid After Substitutions” requires pattern matching and substitution.

Despite these differences, they share the core theme of analyzing strings based on their patterns. Out of the two, “Detect Capital” is simpler due to its straightforward condition checks, while “Check If Word Is Valid After Substitutions” is more complex due to the repetitive pattern recognition involved.

Language Agnostic Coding Drills

Dissecting the code into distinct coding concepts:
a. Variable Initialization: Here count = 0 is an instance of variable initialization. This is an essential concept in virtually all programming languages. Variables serve as placeholders for data that can be used for computation and other operations.
b. Conditional Statements: The use of if and else to execute specific blocks of code based on a condition is a fundamental control structure in programming.
c. String Length Calculation: len(word) is used to calculate the length of the string, which is a key concept in string manipulation.
d. Loops: The for loop used in the code is a basic control structure for iterating over data sequences or for repeating a block of code a specified number of times.
e. String Operations: In the code, word[i].isupper() is used to determine whether a character in a string is uppercase or not.
f. Comparison and Logical Operators: The operators ==, and, or are used to compare values and to form compound logical expressions.
g. Return Statement: The return keyword is used to exit a function and return a value.
Order of increasing difficulty and descriptions:
a. Variable Initialization - Very easy: this is a fundamental concept that’s typically one of the first things learned when starting with programming.
b. String Length Calculation - Easy: it’s a standard built-in function for strings in Python.
c. Conditional Statements - Easy to medium: while the concept is simple, forming complex conditional statements may require more thinking and understanding of the problem.
d. Comparison and Logical Operators - Medium: requires understanding of boolean logic and the precedence and associativity rules for operators.
e. Return Statement - Medium: involves understanding function control flow and the effect of return on it.
f. Loops - Medium: requires understanding of iteration and control flow.
g. String Operations - Medium to hard: these operations can be as simple as accessing individual characters or as complex as parsing and manipulating strings with built-in and user-defined functions.
Problem-solving approach leading to the final solution:

The function first checks whether the length of the word is 1, if it’s so it immediately returns True as a single character is always considered as correct capital usage.

Then, it iterates through each character in the word to count the number of uppercase characters. This is accomplished through a for loop and the use of isupper() function which returns True if a character is uppercase and False otherwise.

Next, the function checks if the count of uppercase characters is one and the first character of the word is uppercase. If it’s the case, it returns True because it means only the first character is uppercase which is correct according to the problem statement.

Afterwards, the function checks if the count of uppercase characters is either 0 or equal to the length of the word. If this condition is true, it returns True because it means all characters are either lowercase or uppercase which are both correct according to the problem statement.

If none of the above conditions are met, it returns False which means the usage of capitals is not correct. Each of these steps is a ‘coding drill’ that can be practiced and then combined to form the final solution.

Targeted Drills in Python

Python coding drills for each identified concept:
a. Variable Initialization
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count = 0
This is a simple initialization of a variable count with an integer value 0.
b. String Length Calculation
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word = "Hello" length = len(word) print(length) # Outputs: 5
Here we calculate the length of a string using len() function in Python.
c. Conditional Statements
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num = 10 if num > 5: print("Greater than 5") else: print("Not greater than 5")
This is a simple conditional statement which checks if num is greater than 5.
d. Comparison and Logical Operators
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a, b = 5, 10 if a < b and b > 7: print("Both conditions are True")
This illustrates the use of comparison operators (<, >) and a logical operator (and).
e. Return Statement
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def add_numbers(a, b): return a + b sum = add_numbers(5, 10) print(sum) # Outputs: 15
This is a simple function that adds two numbers and returns the result.
f. Loops
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for i in range(5): print(i)
A simple for loop in Python that prints numbers from 0 to 4.
g. String Operations
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word = "Python" if word[0].isupper(): print("First character is uppercase")
This illustrates the use of the isupper() method to check if the first character in the string is uppercase.
Problem-specific coding drills:
a. Counting Uppercase Characters in a String
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word = "Python" count = sum(1 for char in word if char.isupper()) print(count) # Outputs: 1
This coding drill is crucial for our problem as we need to count the number of uppercase characters in a string.
Integration of these pieces to solve the initial problem:

The problem is solved by integrating these coding drills in the following order:

First, initialize the variable count to store the number of uppercase characters.
Next, calculate the length of the input string word.
If the length of the word is 1, immediately return True as a single character is always considered correct capital usage.
After that, start a loop to iterate through each character in the word. Inside this loop, if a character is uppercase (determined by isupper() method), increment the count.
Once the loop ends, check if the count of uppercase characters is 1 and the first character is uppercase (again determined by isupper() method). If so, return True.
If the previous condition is not met, check if the count of uppercase characters is 0 or equal to the length of the word. If this is true, return True.
Finally, if none of the conditions are met, return False.