Convert String to Lowercase

Given a string s, convert all uppercase characters in the string to their corresponding lowercase characters and return the resulting string.

Examples:

Input: s = "ABCddE"
Output: "abcdde"
Explanation: A, B, C and E are converted to a, b, c and e thus all uppercase characters of the string converted to lowercase letter.

Input: s = "LMNOppQQ"
Output: "lmnoppqq"
Explanation: L, M, N, O, and Q are converted to l, m, n, o and q thus all uppercase characters of the string converted to lowercase letter.

Using Inbuilt Function - O(n) Time and O(1) Space

Most programming languages provide a built-in function to convert characters or strings to lowercase. The idea is to use this function to transform every uppercase character into its lowercase equivalent.

• Traverse the string.
• Convert each character to lowercase using the built-in function.
• Return the modified string.

#include <bits/stdc++.h>
using namespace std;

// Function to convert a string to lowercase
string toLower(string& s)
{
    // Convert the entire string to lowercase
    transform(s.begin(), s.end(), s.begin(), ::tolower);
    return s;
}

int main()
{
    string s = "GeEkS FoR GeEkS";
    cout << toLower(s) << endl;
    return 0;
}

class GFG {

    // Function to convert a string to lowercase
    static String toLower(String s)
    {
        // Convert the entire string to lowercase
        return s.toLowerCase();
    }

    public static void main(String[] args)
    {
        String s = "GeEkS FoR GeEkS";

        System.out.println(toLower(s));
    }
}

# Function to convert a string to lowercase
def toLower(s):

    # Return the lowercase version of the string
    return s.lower()

# Driver Code
if __name__ == "__main__":
    s = "GeEkS FoR GeEkS"

    print(toLower(s))

using System;

class GFG {
    
    // Function to convert a string to lowercase
    static string toLower(string s)
    {
        // Convert the entire string to lowercase
        return s.ToLower();
    }

    static void Main()
    {
        string s = "GeEkS FoR GeEkS";

        Console.WriteLine(toLower(s));
    }
}

// Function to convert a string to lowercase
function toLower(s)
{
    // Convert the entire string to lowercase
    return s.toLowerCase();
}

// Driver Code
let s = "GeEkS FoR GeEkS";

console.log(toLower(s));

geeks for geeks

Converting Characters Manually - O(n) Time and O(1) Space

The ASCII values of uppercase and lowercase English letters differ by 32.

• 'A' = 65, 'a' = 97
• 'B' = 66, 'b' = 98

Thus, for every uppercase letter, adding 32 converts it to its lowercase counterpart.

• Traverse the string character by character.
• If the current character lies between 'A' and 'Z', add ('a' - 'A') (i.e., 32) to it.
• Leave all other characters unchanged.
• Return the modified string.

#include <bits/stdc++.h>
using namespace std;

// Function to convert a string to lowercase
string toLower(string s)
{
    // Traverse each character
    for (char &ch : s)
    {
        // Check if the current character is an
        // uppercase letter
        if (ch >= 'A' && ch <= 'Z')
        {
            // Convert it to lowercase
            ch = ch + ('a' - 'A');
        }
    }
    return s;
}

int main()
{
    string s = "GeEkS FoR GeEkS";
    cout << toLower(s) << endl;
    return 0;
}

class GFG {

    // Function to convert a string to lowercase
    static String toLower(String s)
    {
        // Convert the string into a character array
        char[] arr = s.toCharArray();

        // Traverse each character
        for (int i = 0; i < arr.length; i++) {

            // Check if the current character is an
            // uppercase letter
            if (arr[i] >= 'A' && arr[i] <= 'Z') {

                // Convert it to lowercase
                arr[i] = (char)(arr[i] + ('a' - 'A'));
            }
        }

        // Convert the character array back to a string
        return new String(arr);
    }

    public static void main(String[] args)
    {
        String s = "GeEkS FoR GeEkS";

        System.out.println(toLower(s));
    }
}

# Function to convert a string to lowercase
def toLower(s):

    # Convert the string into a list of characters
    s = list(s)

    # Traverse each character
    for i in range(len(s)):

        # Check if the current character is an uppercase letter
        if 'A' <= s[i] <= 'Z':

            # Convert it to lowercase
            s[i] = chr(ord(s[i]) + (ord('a') - ord('A')))

    # Convert the character list back to a string
    return "".join(s)

# Driver Code
if __name__ == "__main__":
    s = "GeEkS FoR GeEkS"

    print(toLower(s))

using System;

class GFG {
    
    // Function to convert a string to lowercase
    static string toLower(string s)
    {
        // Convert the string into a character array
        char[] arr = s.ToCharArray();

        // Traverse each character
        for (int i = 0; i < arr.Length; i++) {
            // Check if the current character is an
            // uppercase letter
            if (arr[i] >= 'A' && arr[i] <= 'Z') {
                // Convert it to lowercase
                arr[i] = (char)(arr[i] + ('a' - 'A'));
            }
        }

        // Convert the character array back to a string
        return new string(arr);
    }

    static void Main()
    {
        string s = "GeEkS FoR GeEkS";

        Console.WriteLine(toLower(s));
    }
}

// Function to convert a string to lowercase
function toLower(s)
{
    // Convert the string into an array of characters
    let arr = s.split("");

    // Traverse each character
    for (let i = 0; i < arr.length; i++) {

        // Check if the current character is an uppercase
        // letter
        if (arr[i] >= "A" && arr[i] <= "Z") {

            // Convert it to lowercase
            arr[i] = String.fromCharCode(
                arr[i].charCodeAt(0)
                + ("a".charCodeAt(0) - "A".charCodeAt(0)));
        }
    }

    // Convert the character array back to a string
    return arr.join("");
}

// Driver Code
let s = "GeEkS FoR GeEkS";

console.log(toLower(s));

geeks for geeks