# Convert characters of a string to opposite case

Last Updated : 17 Oct, 2023

Given a string, convert the characters of the string into the opposite case,i.e. if a character is the lower case then convert it into upper case and vice-versa.

Examples:

Input : geeksForgEeks
Output : GEEKSfORGeEKS
Input : hello every one
Output : HELLO EVERY ONE

ASCII values  of alphabets: A – Z = 65 to 90, a – z = 97 to 122

Steps:

1. Take one string of any length and calculate its length.
2. Scan string character by character and keep checking the index.
• If a character in an index is in lower case, then subtract 32 to convert it into upper case, else add 32 to convert it in lowercase
3. Print the final string.

Implementation:

## C++

 // CPP program to Convert characters // of a string to opposite case #include using namespace std;   // Function to convert characters // of a string to opposite case void convertOpposite(string& str) {     int ln = str.length();       // Conversion according to ASCII values     for (int i = 0; i < ln; i++) {         if (str[i] >= 'a' && str[i] <= 'z')             // Convert lowercase to uppercase             str[i] = str[i] - 32;         else if (str[i] >= 'A' && str[i] <= 'Z')             // Convert uppercase to lowercase             str[i] = str[i] + 32;     } }   // Driver function int main() {     string str = "GeEkSfOrGeEkS";       // Calling the Function     convertOpposite(str);       cout << str;     return 0; }

## C

 // C program to Convert characters // of a string to opposite case   #include #include   // Function to convert characters // of a string to opposite case void convertOpposite(char* str) {     int ln = strlen(str);       // Conversion according to ASCII values     for (int i = 0; i < ln; i++) {         if (str[i] >= 'a' && str[i] <= 'z')             // Convert lowercase to uppercase             str[i] = str[i] - 32;         else if (str[i] >= 'A' && str[i] <= 'Z')             // Convert uppercase to lowercase             str[i] = str[i] + 32;     } }   // Driver function int main() {     char str[] = "GeEkSfOrGeEkS";       // Calling the Function     convertOpposite(str);       printf("%s", str);     return 0; }

## Java

 // Java program to Convert characters // of a string to opposite case class Test {       // Method to convert characters     // of a string to opposite case     static void convertOpposite(StringBuffer str)     {         int ln = str.length();           // Conversion using predefined methods         for (int i = 0; i < ln; i++) {             Character c = str.charAt(i);             if (Character.isLowerCase(c))                 str.replace(i, i + 1,                             Character.toUpperCase(c) + "");             else                 str.replace(i, i + 1,                             Character.toLowerCase(c) + "");         }     }       public static void main(String[] args)     {         StringBuffer str             = new StringBuffer("GeEkSfOrGeEkS");         // Calling the Method         convertOpposite(str);           System.out.println(str);     } } // This code is contributed by Gaurav Miglani

## Python3

 # Python3 program to Convert characters # of a string to opposite case   # Function to convert characters # of a string to opposite case def convertOpposite(str):     ln = len(str)       # Conversion according to ASCII values     for i in range(ln):         if str[i] >= 'a' and str[i] <= 'z':               # Convert lowercase to uppercase             str[i] = chr(ord(str[i]) - 32)           elif str[i] >= 'A' and str[i] <= 'Z':               # Convert lowercase to uppercase             str[i] = chr(ord(str[i]) + 32)   # Driver code if __name__ == "__main__":     str = "GeEkSfOrGeEkS"     str = list(str)       # Calling the Function     convertOpposite(str)       str = ''.join(str)     print(str)   # This code is contributed by # sanjeev2552

## C#

 // C# program to Convert characters // of a string to opposite case using System; using System.Text;   class GFG{           // Method to convert characters     // of a string to opposite case     static void convertOpposite(StringBuilder str)     {         int ln = str.Length;                       // Conversion according to ASCII values         for (int i=0; i='a' && str[i]<='z')                               //Convert lowercase to uppercase                 str[i] = (char)(str[i] - 32);                               else if(str[i]>='A' && str[i]<='Z')                               //Convert uppercase to lowercase                 str[i] = (char)(str[i] + 32);         }     }           // Driver code     public static void Main()     {         StringBuilder str = new StringBuilder("GeEkSfOrGeEkS");         // Calling the Method         convertOpposite(str);         Console.WriteLine(str);         } } // This code is contributed by PrinciRaj1992



## PHP

 = 'a' && \$str[\$i] <= 'z'){             // Convert lowercase to uppercase             \$str[\$i] = strtoupper(\$str[\$i]);          }         else if (\$str[\$i] >= 'A' && \$str[\$i] <= 'Z'){             // Convert uppercase to lowercase             \$str[\$i] = strtolower(\$str[\$i]);         }     }   return \$str; }   // Driver function \$str = "GeEkSfOrGeEkS";       // Calling the Function echo(convertOpposite(\$str));     // This code is contributed by ksrikanth0498     ?>

Output

gEeKsFoRgEeKs

Time Complexity: O(n)

Note: This program can alternatively be done using C++ inbuilt functions – Character.toLowerCase(char) and Character.toUpperCase(char).

Approach 2: The problem can be solved using letter case toggling. Follow the below steps to solve the problem:

• Traverse the given string S.
• For each character, Si, do Si =  Si ^ (1 << 5).
• Si ^ (1 << 5) toggles the 5th bit which means 97 will become 65 and 65 will become 97:
• 65 ^ 32 = 97
• 97 ^ 32 = 65
• Print the string after all operations

Below is the implementation of the above approach:

## C++

 // C++ program to toggle all characters #include using namespace std;   // Function to toggle characters void toggleChars(string& S) {     for (auto& it : S) {         if (isalpha(it)) {             it ^= (1 << 5);         }     } }   // Driver code int main() {     string S = "GeKf@rGeek\$";     toggleChars(S);     cout << "String after toggle " << endl;     cout << S << endl;     return 0; }   // Code contributed by koulick_sadhu

## C

 // C program to toggle all characters   #include #include   // Function to toggle characters void toggleChars(char* S) {     while (*S) {         if (isalpha(*S)) {             *S ^= (1 << 5);         }         ++S;     } }   // Driver code int main() {     char S[] = "GeKf@rGeek\$";     toggleChars(S);     printf("String after toggle:\n%s\n", S);     return 0; }

## Java

 // Java program to toggle all characters import java.util.*;   class GFG {       static char[] S = "GeKf@rGeek\$".toCharArray();       // Function to toggle characters     static void toggleChars()     {         for (int i = 0; i < S.length; i++) {             if (Character.isAlphabetic(S[i])) {                 S[i] ^= (1 << 5);             }         }     }       // Driver code     public static void main(String[] args)     {         toggleChars();         System.out.print("String after toggle "                          + "\n");         System.out.print(String.valueOf(S));     } }   // This code is contributed by Amit Katiyar

## Python3

 # python program for the same approach def isalpha(input):     input_char = ord(input[0])       # CHECKING FOR ALPHABET     if((input_char >= 65 and input_char <= 90) or (input_char >= 97 and input_char <= 122)):         return True     else:         return False   # Function to toggle characters     def toggleChars(S):     s = ""       for it in range(len(S)):           if(isalpha(S[it])):             s += chr(ord(S[it]) ^ (1 << 5))         else:             s += S[it]       return s     # Driver code S = "GeKf@rGeek\$" print(f"String after toggle {toggleChars(S)}")   # This code is contributed by shinjanpatra

## C#

 // C# program to toggle all characters using System;   class GFG {       static char[] S = "GeKf@rGeek\$".ToCharArray();       // Function to toggle characters     static void toggleChars()     {         for (int i = 0; i < S.Length; i++) {             if (char.IsLetter(S[i])) {                 S[i] = (char)((int)(S[i]) ^ (1 << 5));             }         }     }       // Driver code     public static void Main(String[] args)     {         toggleChars();         Console.Write("String after toggle "                       + "\n");         Console.Write(String.Join("", S));     } }   // This code is contributed by Princi Singh

## Javascript

   // This code is contributed by Akshit Saxena

Output

String after toggle
gEkF@RgEEK\$

Time Complexity: O(n)

Approach : Using isupper() and islower(),upper() and lower().

Initialize an empty string.Iterate a for loop over the given string and check each character whether is lowercase or uppercase using isupper() and islower().If lowercase converts the character to uppercase using upper() and append to empty string, similarly with uppercase.

## C++

 // C++ program to Convert characters // of a string to opposite case   #include using namespace std;   int main() {       string str = "GeEkSfOrGeEkS";     string x = "";     for (int i = 0; i < str.length(); i++) {         char ch = str[i];         if (isupper(ch))             x += tolower(ch);         else             x += toupper(ch);     }     cout << x << endl;     return 0; }   // This code is contributed by lokeshmvs21.

## C

 // C program to Convert characters // of a string to opposite case   #include #include #include   int main() {     char str[] = "GeEkSfOrGeEkS";     char x[100];     for (int i = 0; i < strlen(str); i++) {         char ch = str[i];         if (isupper(ch))             x[i] = tolower(ch);         else             x[i] = toupper(ch);     }     x[strlen(str)] = '\0';     printf("%s\n", x);     return 0; }

## Java

 // Java program to Convert characters // of a string to opposite case import java.io.*;   class GFG {   public static void main(String[] args)   {     String str = "GeEkSfOrGeEkS";     String x = "";     for (int i = 0; i < str.length(); i++) {       char ch = str.charAt(i);       if (Character.isUpperCase(ch))         x += Character.toLowerCase(ch);       else         x += Character.toUpperCase(ch);     }     System.out.println(x);   } }   // This code is contributed by karandeep1234.

## Python3

 # Python3 program to Convert characters # of a string to opposite case   str = "GeEkSfOrGeEkS" x="" for i in str:     if(i.isupper()):         x+=i.lower()     else:         x+=i.upper() print(x)

## C#

 // C# program to Convert characters // of a string to opposite case using System;   public class GFG {     static public void Main()   {       // Code     string str = "GeEkSfOrGeEkS";     string x = "";     for (int i = 0; i < str.Length; i++) {       char ch = str[i];       if (Char.IsUpper(ch)) {         x += Char.ToLower(ch);       }       else {         x += Char.ToUpper(ch);       }     }     Console.WriteLine(x);   } }   // This code is contributed by lokeshmvs21.

## Javascript

 // Javascript program to Convert characters // of a string to opposite case        let str = "GeEkSfOrGeEkS";     let x = "";     for (let i = 0; i < str.length; i++) {       let ch = str[i];       if(str.charAt(i) === str.charAt(i).toUpperCase())         x += str.charAt(i).toLowerCase(ch);       else         x += str.charAt(i).toUpperCase(ch);     }     console.log(x);           // This code is contributed by garg28harsh.

Output

gEeKsFoRgEeKs

Approach : Using index() method

## C++

 // C++ program to Convert characters // of a string to opposite case #include using namespace std;   int main() {     string str = "GeEkSfOrGeEkS";     string x = "";     string upperalphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";     string loweralphabets = "abcdefghijklmnopqrstuvwxyz";     for (int i = 0; i < str.length(); i++) {         char ch = str[i];         if (upperalphabets.find(ch) != -1) {             x += loweralphabets[upperalphabets.find(ch)];         }         else {             x += upperalphabets[loweralphabets.find(ch)];         }     }     cout << x << endl;     return 0; } // This code is contributed by Prajwal Kandekar

## C

 // C program to Convert characters // of a string to opposite case #include #include   int main() {     char str[] = "GeEkSfOrGeEkS";     char x[100] = "";     char upperalphabets[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";     char loweralphabets[] = "abcdefghijklmnopqrstuvwxyz";     int i, j;     for (i = 0; i < strlen(str); i++) {         char ch = str[i];         if (strchr(upperalphabets, ch)) {             j = strchr(upperalphabets, ch) - upperalphabets;             x[i] = loweralphabets[j];         }         else {             j = strchr(loweralphabets, ch) - loweralphabets;             x[i] = upperalphabets[j];         }     }     printf("%s\n", x);     return 0; }

## Java

 // Java program to Convert characters // of a string to opposite case   public class GFG {   public static void main(String[] args)   {     String str = "GeEkSfOrGeEkS";     String x = "";     String upperalphabets       = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";     String loweralphabets       = "abcdefghijklmnopqrstuvwxyz";     for (int i = 0; i < str.length(); i++) {       char ch = str.charAt(i);       if (upperalphabets.indexOf(ch) != -1) {         x += loweralphabets.charAt(           upperalphabets.indexOf(ch));       }       else {         x += upperalphabets.charAt(           loweralphabets.indexOf(ch));       }     }     System.out.println(x);   } }   // This Code is contributed by karandeep1234

## Python3

 # Python3 program to Convert characters # of a string to opposite case   str = "GeEkSfOrGeEkS" x="" upperalphabets="ABCDEFGHIJKLMNOPQRSTUVWXYZ" loweralphabets="abcdefghijklmnopqrstuvwxyz" for i in str:     if i in upperalphabets:         x+=loweralphabets[upperalphabets.index(i)]     else:         x+=upperalphabets[loweralphabets.index(i)] print(x)

## C#

 // C# program to Convert characters // of a string to opposite case using System;   public class GFG {   public static void Main(string[] args)   {     string str = "GeEkSfOrGeEkS";     string x = "";     string upperalphabets       = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";     string loweralphabets       = "abcdefghijklmnopqrstuvwxyz";     for (int i = 0; i < str.Length; i++) {       char ch = str[i];       if (upperalphabets.IndexOf(ch) != -1) {         x += loweralphabets[upperalphabets.IndexOf(           ch)];       }       else {         x += upperalphabets[loweralphabets.IndexOf(           ch)];       }     }     Console.WriteLine(x);   } }   // This Code is contributed by karandeep1234

## Javascript

 // Javascript program to Convert characters // of a string to opposite case         let str = "GeEkSfOrGeEkS";     let x = "";     let upperalphabets       = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";     let loweralphabets       = "abcdefghijklmnopqrstuvwxyz";     for (let i = 0; i < str.length; i++) {       let ch = str[i];       if (upperalphabets.indexOf(ch) != -1) {         x += loweralphabets[upperalphabets.indexOf(ch)];       }       else {         x += upperalphabets[loweralphabets.indexOf(ch)];       }     }     console.log(x);   // This code is contributed by garg28harsh.

Output

gEeKsFoRgEeKs

Another Approach:-

• In this approach we will use transform function
• What transform function do is that it convert the case of a string into upper case or lower case without using any other extra space or string.
• In this approach we will just traverse the string and check the case of the character.
• If the character is in upper case then we will use transform function to convert it into lower case.
• else we will convert in into upper case
• Below is the implementation of the above approach.

Implementation:-

## C++

 // C++ program to Convert characters // of a string to opposite case #include using namespace std; int main() {     string str = "GeEkSfOrGeEkS";     for (int i = 0; i < str.length(); i++) {           if(isupper(str[i])){               transform(str.begin()+i, str.begin()+i+1, str.begin()+i, ::tolower);         }         else{               transform(str.begin()+i, str.begin()+i+1, str.begin()+i, ::toupper);         }     }     cout << str << endl;     return 0; } // This code is contributed by shubhamrajput6156

## C

 // C program to Convert characters // of a string to opposite case   #include #include #include   int main() {     char str[] = "GeEkSfOrGeEkS";     int len = strlen(str);     for (int i = 0; i < len; i++) {         if (isupper(str[i])) {             str[i] = tolower(str[i]);         }         else {             str[i] = toupper(str[i]);         }     }     printf("%s\n", str);     return 0; }

## Java

 import java.util.*;   public class Main {     public static void main(String[] args) {         String str = "GeEkSfOrGeEkS";         StringBuilder sb = new StringBuilder(str);                   for (int i = 0; i < sb.length(); i++) {             if (Character.isUpperCase(sb.charAt(i))) {                 sb.setCharAt(i, Character.toLowerCase(sb.charAt(i)));             } else {                 sb.setCharAt(i, Character.toUpperCase(sb.charAt(i)));             }         }                   str = sb.toString();         System.out.println(str);     } }

## Python3

 # Python program to Convert characters # of a string to opposite case   str = "GeEkSfOrGeEkS"   for i in range(len(str)):     if str[i].isupper():         str = str[:i] + str[i].lower() + str[i+1:]     else:         str = str[:i] + str[i].upper() + str[i+1:]   print(str)

## C#

 // C# program to Convert characters // of a string to opposite case using System;   class GFG {     public static void Main() {         string str = "GeEkSfOrGeEkS";       for (int i = 0; i < str.Length; i++) {           // If the character is upper case, convert it to lower case           if (Char.IsUpper(str[i])) {           str = str.Remove(i, 1).Insert(i, Char.ToLower(str[i]).ToString());       }       // If the character is lower case, convert it to upper case       else {           str = str.Remove(i, 1).Insert(i, Char.ToUpper(str[i]).ToString());       }     }     Console.WriteLine(str);     } }

## Javascript

 let str = "GeEkSfOrGeEkS"; for (let i = 0; i < str.length; i++) {   if (str[i] === str[i].toUpperCase()) {     str = str.slice(0, i) + str[i].toLowerCase() + str.slice(i + 1);   } else {     str = str.slice(0, i) + str[i].toUpperCase() + str.slice(i + 1);   } } console.log(str);   // THIS CODE IS CONTRIBUTED BY CHANDAN AGARWAL

Output

gEeKsFoRgEeKs

Time Complexity:- O(N) Where N is length of String

Auxiliary Space:- O(1)

Another Approach:

In this implementation, we initialize a pointer p to the start of the string str. We then use a while loop to iterate through the string by checking if the character p points to is the null character (‘\0’). Inside the loop, we use the same logic as the previous implementation, but instead of accessing the array element at index i, we use the dereference operator * to access the value that p points to. After updating the character at the current position, we increment the pointer p to point to the next character in the string.

## C++

 #include #include #include   int main() {     char str[] = "GeEkSfOrGeEkS";     char* p = str;  // initialize pointer to start of string     while (*p != '\0') {         if (isupper(*p)) {             *p = tolower(*p);         }         else {             *p = toupper(*p);         }         p++;  // move pointer to next character     }     printf("%s\n", str);     return 0; }

## Java

 import java.io.*; public class GFG {     public static void main(String[] args) {         String str = "GeEkSfOrGeEkS";         char[] charArray = str.toCharArray();       // Convert the string to a character array         for (int i = 0; i < charArray.length; i++) {             if (Character.isUpperCase(charArray[i])) {                 charArray[i] = Character.toLowerCase(charArray[i]);               // Convert uppercase to lowercase             } else {                 charArray[i] = Character.toUpperCase(charArray[i]);               // Convert lowercase to uppercase             }         }         String toggledStr = new String(charArray);       // Convert the character array back to  string         System.out.println(toggledStr);     } }

## Python3

 str_value = "GeEkSfOrGeEkS" p = 0  # Initialize an index variable to start of string str_list = list(str_value)  # Convert the string to a list of characters   while p < len(str_list):     if str_list[p].isupper():         str_list[p] = str_list[p].lower()     else:         str_list[p] = str_list[p].upper()     p += 1  # Move index to the next character   result = ''.join(str_list)  # Convert the list back to a string print(result)   # This code is contributed by akshitaguprzj3

## C#

 using System;   class Program {     static void Main(string[] args)     {         string str = "GeEkSfOrGeEkS";         char[] charArray             = str.ToCharArray(); // Convert the string to a                                  // character array           for (int i = 0; i < charArray.Length; i++) {             if (char.IsUpper(                     charArray[i])) // Check if the character                                    // is uppercase             {                 charArray[i] = char.ToLower(                     charArray[i]); // Convert to lowercase             }             else {                 charArray[i] = char.ToUpper(                     charArray[i]); // Convert to uppercase             }         }           string modifiedStr = new string(             charArray); // Convert the character array back                         // to a string         Console.WriteLine(modifiedStr);     } }

## Javascript

 // JavaScript Program for the above approach const str = "GeEkSfOrGeEkS"; let result = ""; for (let i = 0; i < str.length; i++) {   const char = str.charAt(i);   if (char === char.toUpperCase()) {       result += char.toLowerCase();   } else {       result += char.toUpperCase();   } } console.log(result); // THIS CODE IS CONTRIBUTED BY PIYUSH AGARWAL

Output

gEeKsFoRgEeKs

Time Complexity:- O(n) Where N is length of input String

Auxiliary Space:- O(1)

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