To Lower Case

Problem Statement

In this problem, we are given a string s that can contain both uppercase and lowercase letters among other printable ASCII characters. The task is to transform all uppercase letters in the string to their corresponding lowercase versions. For characters in the string that are already lowercase or aren't alphabetic (such as numbers or punctuation marks), they should remain unchanged. The function needs to return the new string where every uppercase letter has been replaced with its lowercase counterpart.

Examples

Example 1

Input:

s = "Hello"

Output:

"hello"

Example 2

Input:

s = "here"

Output:

"here"

Example 3

Input:

s = "LOVELY"

Output:

"lovely"

Constraints

• 1 <= s.length <= 100
• s consists of printable ASCII characters.

Approach and Intuition

The problem requires converting all uppercase letters in a string to their lowercase equivalents and is a straightforward process:

1. Read the input string s which is guaranteed by the constraints to be at least 1 character long and no more than 100 characters, and consists of printable ASCII characters.

2. Traverse each character in the string:

   • If the character is an uppercase letter (from 'A' to 'Z'), convert it to its corresponding lowercase letter (from 'a' to 'z').
   • If the character is not an uppercase letter, it remains unchanged.

3. Construct a new string with these updated characters.

4. Return the transformed string.

This approach can be implemented efficiently within the given constraints and with the simplicity of the task, the conversion can be done in a single pass through the string, ensuring a time complexity of O(n), where n is the length of the string. By ensuring each character is checked and potentially transformed once, we achieve a direct and optimal solution. This process leverages the basic ASCII value conversions or string manipulation functions provided in most programming languages, making the implementation straightforward.

Solutions

class Solution {
    public boolean checkUpperCase(char c) {
        return 'A' <= c && c <= 'Z';
    }

    public char convertToLower(char c) {
        return (char) ((int)c | 32);
    }

    public String convertToLowerCase(String str) {
        StringBuilder result = new StringBuilder();
        for (char ch : str.toCharArray()) {
            result.append(checkUpperCase(ch) ? convertToLower(ch) : ch);
        }
        return result.toString();
    }
}