Convert characters of a string to opposite case

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

Input : geeksForgEeks

Input : hello every one

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

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


// CPP program to Convert characters 
// of a string to opposite case
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
    cout << str;
    return 0;


// 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)+"");
                str.replace(i, i+1, Character.toLowerCase(c)+"");
     public static void main(String[] args) 
         StringBuffer str = new StringBuffer("GeEkSfOrGeEkS");
         // Calling the Method
// This code is contributed by Gaurav Miglani



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

This article is contributed by Rishabh Jain. If you like GeeksforGeeks and would like to contribute, you can also write an article using or mail your article to See your article appearing on the GeeksforGeeks main page and help other Geeks.

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