A string is a sequence of characters. In this article, you'll learn how to convert the characters of a string to the opposite cases. You'll also learn how to solve this problem using the most popular programming languages like C++, Python, C, and JavaScript.

Problem Statement

You're given a string. You need to convert all the characters of this string to the opposite cases.

Example 1: Let str = "Welcome to MUO"

String after converting all the characters to the opposite cases = "wELCOME TO muo"

Thus, the output is "wELCOME TO muo".

Example 2: Let str = "Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair."

String after converting all the characters to the opposite cases = "fUZZY wUZZY WAS A BEAR. fUZZY wUZZY HAD NO HAIR."

Thus, the output is "fUZZY wUZZY WAS A BEAR. fUZZY wUZZY HAD NO HAIR.".

Example 3: Let str = "Tom threw Tim three thumbtacks"

String after converting all the characters to the opposite cases = "tOM THREW tIM THREE THUMBTACKS"

Thus, the output is "tOM THREW tIM THREE THUMBTACKS".

Related: How to Check if Two Strings Are Anagrams of Each Other

C++ Program to Convert Characters of a String to the Opposite Cases

Below is the C++ program to convert the characters of a string to the opposite cases:

        // C++ program to convert characters of string to opposite case
#include <iostream>
using namespace std;

string convertString(string& str)
{
 int length = str.length();
 for (int i = 0; i < length; i++)
 {
 // If the character is in lowercase,
 // convert it to uppercase
 if (str[i] >= 'a' && str[i] <= 'z')
 {
 str[i] = str[i] - 32;
 }
 // If the character is in uppercase,
 // convert it to lowercase
 else if (str[i] >= 'A' && str[i] <= 'Z')
 {
 str[i] = str[i] + 32;
 }
 }
 return str;
}

int main()
{
 string str1 = "Welcome to MUO";
 cout << "Original String 1:" << endl;
 cout << str1 << endl;
 str1 = convertString(str1);
 cout << "Converted String 1:" << endl;
 cout << str1 << endl;

 string str2 = "Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair.";
 cout << "Original String 2:" << endl;
 cout << str2 << endl;
 str2 = convertString(str2);
 cout << "Converted String 2:" << endl;
 cout << str2 << endl;

 string str3 = "Tom threw Tim three thumbtacks";
 cout << "Original String 3:" << endl;
 cout << str3 << endl;
 str3 = convertString(str3);
 cout << "Converted String 3:" << endl;
 cout << str3 << endl;

return 0;
}
    

Output:

        Original String 1:
Welcome to MUO
Converted String 1:
wELCOME TO muo
Original String 2:
Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair.
Converted String 2:
fUZZY wUZZY WAS A BEAR. fUZZY wUZZY HAD NO HAIR.
Original String 3:
Tom threw Tim three thumbtacks
Converted String 3:
tOM THREW tIM THREE THUMBTACKS
    

Related: How to Validate Strings Using Boolean Methods in Python

Python Program to Convert Characters of a String to the Opposite Cases

Below is the Python program to convert the characters of a string to the opposite cases:

        # Python program to convert characters of string to opposite case
def convertString(str):
    length = len(str)
    result = ""
    for i in range(length):
        # If the character is in lowercase,
        # convert it to uppercase
        if str[i].islower():
            result += str[i].upper()
        # If the character is in uppercase,
        # convert it to lowercase
        elif str[i].isupper():
            result += str[i].lower()
        else:
            result += str[i]
    return result


str1 = "Welcome to MUO"
print("Original String 1:")
print(str1)
print("Converted String 1:")
print(convertString(str1))

str2 = "Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair."
print("Original String 2:")
print(str2)
print("Converted String 2:")
print(convertString(str2))

str3 = "Tom threw Tim three thumbtacks"
print("Original String 3:")
print(str3)
print("Converted String 3:")
print(convertString(str3))

    

Output:

        Original String 1:
Welcome to MUO
Converted String 1:
wELCOME TO muo
Original String 2:
Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair.
Converted String 2:
fUZZY wUZZY WAS A BEAR. fUZZY wUZZY HAD NO HAIR.
Original String 3:
Tom threw Tim three thumbtacks
Converted String 3:
tOM THREW tIM THREE THUMBTACKS
    

JavaScript Program to Convert Characters of a String to the Opposite Cases

Below is the JavaScript program to convert the characters of a string to the opposite cases:

        // JavaScript program to convert characters of string to opposite case

function convertString(str) {
 var length = str.length;
 var result = "";
 for (let i = 0; i < str.length; i++) {
 // If the character is in lowercase,
 // convert it to uppercase
 if (str.charAt(i) === str.charAt(i).toLowerCase()) {
 result += str.charAt(i).toUpperCase();
 // If the character is in uppercase,
 // convert it to lowercase
 } else if (str.charAt(i) === str.charAt(i).toUpperCase()) {
 result += str.charAt(i).toLowerCase()
 } else {
 result += str.charAt(i);
 }
 }
 return result;
}

var str1 = "Welcome to MUO";
document.write("Original String 1:" + "
");
document.write(str1 + "
");
str1 = convertString(str1);
document.write("Converted String 1:" + "
");
document.write(str1 + "
");

var str2 = "Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair.";
document.write("Original String 2:" + "
");
document.write(str2 + "
");
str2 = convertString(str2);
document.write("Converted String 2:" + "
");
document.write(str2 + "
");

var str3 = "Tom threw Tim three thumbtacks";
document.write("Original String 3:" + "
");
document.write(str3 + "
");
str3 = convertString(str3);
document.write("Converted String 3:" + "
");
document.write(str3 + "
");
    

Output:

        Original String 1:
Welcome to MUO
Converted String 1:
wELCOME TO muo
Original String 2:
Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair.
Converted String 2:
fUZZY wUZZY WAS A BEAR. fUZZY wUZZY HAD NO HAIR.
Original String 3:
Tom threw Tim three thumbtacks
Converted String 3:
tOM THREW tIM THREE THUMBTACKS

    

Related: JavaScript String Methods You Should Master Today

C Program to Convert Characters of a String to the Opposite Cases

Below is the C program to convert the characters of a string to the opposite cases:

        // C program to convert characters of string to opposite case
#include <stdio.h>
#include <string.h>
#include <stdbool.h>

const char* convertString(char str[])
{
 int length = strlen(str);
 for (int i = 0; i < length; i++)
 {
 // If the character is in lowercase,
 // convert it to uppercase
 if (str[i] >= 'a' && str[i] <= 'z')
 {
 str[i] = str[i] - 32;
 }
 // If the character is in uppercase,
 // convert it to lowercase
 else if (str[i] >= 'A' && str[i] <= 'Z')
 {
 str[i] = str[i] + 32;
 }
 }
 return str;
}

int main()
{
 char str1[] = "Welcome to MUO";
 printf("Original String 1: \⁠n");
 printf("%s \⁠n", str1);
 printf("Converted String 1: \⁠n");
 printf("%s", convertString(str1));

 char str2[] = "Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair.";
 printf("Original String 2: \⁠n");
 printf("%s \⁠n", str2);
 printf("Converted String 2: \⁠n");
 printf("%s", convertString(str2));

 char str3[] = "Tom threw Tim three thumbtacks";
 printf("Original String 3: \⁠n");
 printf("%s \⁠n", str3);
 printf("Converted String 3: \⁠n");
 printf("%s", convertString(str3));

return 0;
}
    

Output:

        Original String 1:
Welcome to MUO
Converted String 1:
wELCOME TO muo
Original String 2:
Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair.
Converted String 2:
fUZZY wUZZY WAS A BEAR. fUZZY wUZZY HAD NO HAIR.
Original String 3:
Tom threw Tim three thumbtacks
Converted String 3:
tOM THREW tIM THREE THUMBTACKS
    

Learn More About String Manipulation

In this article, you learned how to convert characters of the string to opposite cases. Dealing with strings and texts is an integral part of programming. You must know how to manipulate strings.

Python is a solid choice to get started with if you're looking for a language to manipulate strings easily and efficiently.