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Basic String Operations with Implementation

Last Updated : 23 Apr, 2024
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In this post, we will look into some of the basic String operations such as:

  • Accessing characters by index in a string.
  • Inserting character into a String.
  • Modifying character in String
  • Deletion of Character in String
  • Concatenating strings (combining multiple strings into one).
  • Finding the length of a string
  • Comparing strings for equality or lexicographical order

Let us consider the basic String operations one by one.

Accessing characters by index in a string.

To access any character in a String, we need:

  1. A non-empty string (say “str”)
  2. A position/index of the character from where it is to be accessed. (say “k”)

Using these two, the character can be easily accessed using the below syntax:

char ch = str[k];
OR
char ch = str.charAt(k);

Below is the implementation of the above approach:

C++ 
// CPP code for accessing an element by index

#include <iostream>
#include <string>

using namespace std;

// Function to demonstrate insert
char accessCharByIndex(string str, int k)
{

    // return the character at Kth index
    // in the string str
    return str[k];
}

// Driver code
int main()
{
    string str("GeeksforGeeks ");
    int k = 4;
    cout << accessCharByIndex(str, k) << endl;

    return 0;
}
C 
#include <stdio.h>
#include <string.h>

// Function to demonstrate accessing character by index
char accessCharByIndex(char* str, int k)
{
    // Return the character at the kth index in the string
    return str[k];
}

// Driver code
int main()
{
    char str[] = "GeeksforGeeks ";
    int k = 4;
    printf("%c\n", accessCharByIndex(str, k));

    return 0;
}
Java 
public class GFG {
  
    // Function to demonstrate accessCharByIndex
    public static char accessCharByIndex(String str, int k) {
      
        // Return the character at the k-th index in the string str
        return str.charAt(k);
    }

    // Driver code
    public static void main(String[] args) {
        String str = "GeeksforGeeks ";
        int k = 4;
        System.out.println(accessCharByIndex(str, k));
    }
}
Python 
# Function to access an element by index
def access_char_by_index(s, k):
  
    # Return the character at the kth index in the string s
    return s[k]

# Driver code


def main():
    string_value = "GeeksforGeeks "
    index = 4
    print(access_char_by_index(string_value, index))


# Run the main function
if __name__ == "__main__":
    main()
C# 
using System;

class Program {
  
    // Function to access a character by index
    static char AccessCharByIndex(string str, int k)
    {
      
        // Return the character at the k-th index
        return str[k];
    }

    static void Main()
    {
        string str = "GeeksforGeeks ";
        int k = 4;
        Console.WriteLine(AccessCharByIndex(str, k));
    }
}
JavaScript 
// Function to demonstrate access by index
function accessCharByIndex(str, k) {
    // Return the character at the kth index in the string str
    return str[k];
}

// Driver code
let str = "GeeksforGeeks ";
let k = 4;
console.log(accessCharByIndex(str, k));

Output
s

Inserting Character/String into an String.

To insert any Character/String in a String, we need:

  1. A character/string that is to be inserted in the string (say “ch”)
  2. A position/index of the Character/String where it is to be inserted. (say “k”)

Below is the implementation of the above approach:

C++ 
// CPP code for Inserting character/string into an String.
#include <iostream>
#include <string>

using namespace std;

// Function to demonstrate insert
void insertDemo(string str, string ch, int k)
{

    // Inserts ch at kth index of str
    str.insert(k, ch);
    cout << "Modified String : " << str << endl;
}

// Driver code
int main()
{
    string str("GeeksGeeks ");
    string ch = "for";
    int k = 5;

    cout << "Original String : " << str << endl;
    insertDemo(str, ch, k);

    return 0;
}
C 
#include <stdio.h>
#include <string.h>

void insertDemo(char* str, const char* ch, int k) {
    int len1 = strlen(str);
    int len2 = strlen(ch);

    // Shift characters to the right to make space for ch
    for (int i = len1; i >= k; i--) {
        str[i + len2] = str[i];
    }

    // Insert ch at kth index of str
    for (int i = 0; i < len2; i++) {
        str[k + i] = ch[i];
    }

    printf("Modified String: %s\n", str);
}

int main() {
    char str[] = "GeeksGeeks ";
    char ch[] = "for";
    int k = 5;

    printf("Original String: %s\n", str);
    insertDemo(str, ch, k);

    return 0;
}
Java 
public class Main {
    public static void main(String[] args) {
        String str = "GeeksGeeks ";
        String ch = "for";
        int k = 5;

        System.out.println("Original String: " + str);
        insertDemo(str, ch, k);
    }

    // Function to demonstrate insert
    public static void insertDemo(String str, String ch, int k) {
        // Inserts ch at kth index of str
        StringBuilder sb = new StringBuilder(str);
        sb.insert(k, ch);
        String modifiedString = sb.toString();
        System.out.println("Modified String: " + modifiedString);
    }
}
Python 
# Python program for the above approach

# Function to demonstrate insert
def insert_demo(s, ch, k):

    # Inserts ch at kth index of s
    modified_string = s[:k] + ch + s[k:]
    print("Modified String:", modified_string)

# Driver code
if __name__ == "__main__":
    original_string = "GeeksGeeks "
    ch_to_insert = "for"
    index_to_insert = 5

    print("Original String:", original_string)
    insert_demo(original_string, ch_to_insert, index_to_insert)

# This code is contributed by Susobhan Akhuli
C# 
using System;

class Program
{
    // Function to demonstrate insert
    static string InsertDemo(string str, string ch, int k)
    {
        // Inserts ch at kth index of str
        return str.Insert(k, ch);
    }

    // Driver code
    static void Main()
    {
        string str = "GeeksGeeks ";
        string ch = "for";
        int k = 5;

        Console.WriteLine("Original String: " + str);
        string modifiedString = InsertDemo(str, ch, k);
        Console.WriteLine("Modified String: " + modifiedString);
    }
}
JavaScript 
// JavaScript equivalent of the given Java code

// Function to demonstrate insert
function insertDemo(str, ch, k) {
    // Inserts ch at kth index of str
    let modifiedString = str.slice(0, k) + ch + str.slice(k);
    console.log("Modified String: " + modifiedString);
}

// Main function
function main() {
    let str = "GeeksGeeks ";
    let ch = "for";
    let k = 5;

    console.log("Original String: " + str);
    insertDemo(str, ch, k);
}

// Call the main function
main();

Output
Original String : GeeksGeeks 
Modified String : GeeksforGeeks

Modifying character in String

To modify any Character in a String, we need:

  1. A character that is to replaced in the string (say “ch”)
  2. A position/index of the Character where it is to be replaced at. (say “k”)

Below is the implementation of the above approach:

C++ 
#include <iostream>
#include <string>

int main()
{
    // Get the string
    std::string str = "Geeks Gor Geeks";

    // Get the index
    int index = 6;

    // Get the character
    char ch = 'F';

    // Print the original string
    std::cout << "Original String = " << str << std::endl;

    str.replace(index, 1, 1, ch);

    // Print the modified string
    std::cout << "Modified String = " << str << std::endl;

    return 0;
}
C 
#include <stdio.h>
#include <string.h>

int main()
{
    // Define the string
    char str[] = "Geeks Gor Geeks";

    // Define the index
    int index = 6;

    // Define the character
    char ch = 'F';

    // Print the original string
    printf("Original String = %s\n", str);

    // Modify the string
    str[index] = ch;

    // Print the modified string
    printf("Modified String = %s\n", str);

    return 0;
}
Java 
public class GFG {

    public static void main(String args[])
    {

        // Get the String
        String str = "Geeks Gor Geeks";

        // Get the index
        int index = 6;

        // Get the character
        char ch = 'F';

        // Print the original string
        System.out.println("Original String = " + str);

        str = str.substring(0, index) + ch
            + str.substring(index + 1);

        // Print the modified string
        System.out.println("Modified String = " + str);
    }
}
Python 
# Function to replace a character at a specific index in a string
def replace_character_at_index(string, index, new_character):

    # Convert string to list of characters to allow modification
    string_list = list(string)

    # Replace character at the specified index
    string_list[index] = new_character

    # Convert back to string and return
    return ''.join(string_list)

# Main function


def main():
    # Original string
    original_string = "Geeks Gor Geeks"

    # Index to replace character
    index = 6

    # New character
    new_character = 'F'

    # Print original string
    print("Original String =", original_string)

    # Replace character at the specified index
    modified_string = replace_character_at_index(
        original_string, index, new_character)

    # Print modified string
    print("Modified String =", modified_string)


# Entry point of the program
if __name__ == "__main__":
    main()
C# 
using System;

public class GFG
{
    public static void Main()
    {
        // Get the String
        string str = "Geeks Gor Geeks";

        // Get the index
        int index = 6;

        // Get the character
        char ch = 'F';

        // Print the original string
        Console.WriteLine("Original String = " + str);

        // Modify the string
        str = str.Substring(0, index) + ch + str.Substring(index + 1);

        // Print the modified string
        Console.WriteLine("Modified String = " + str);
    }
}
JavaScript 
let str = "Geeks Gor Geeks"; // Get the string
let index = 6; // Get the index
let ch = 'F'; // Get the character

console.log("Original String = " + str); // Print the original string

// Modify the string
str = str.substr(0, index) + ch + str.substr(index + 1);

console.log("Modified String = " + str); // Print the modified string

Output
Original String = Geeks Gor Geeks
Modified String = Geeks For Geeks

Deletion of character in String

To delete any Character in a String, we need:

  • A character that is to deleted in the string (say “ch”)

Below is the implementation of the above approach:

C++ 
// C++ program to remove a particular character
// from a string.
#include <bits/stdc++.h>
using namespace std;

void removeChar(char* s, char c)
{

    int j, n = strlen(s);
    for (int i = j = 0; i < n; i++)
        if (s[i] != c)
            s[j++] = s[i];

    s[j] = '\0';
}

int main()
{
    char s[] = "geeksforgeeks";
    removeChar(s, 'g');
    cout << s;
    return 0;
}
C 
#include <stdio.h>
#include <string.h>

void removeChar(char* s, char c) {
    int i, j, n = strlen(s);
    for (i = j = 0; i < n; i++) {
        if (s[i] != c) {
            s[j++] = s[i];
        }
    }
    s[j] = '\0';
}

int main() {
    char s[] = "geeksforgeeks";
    removeChar(s, 'g');
    printf("%s", s);
    return 0;
}
Java 
public class Main {
       // Function to remove a particular character 
      // from a character array
     // Parameters:
    // - s: the character array from which 
    // the character will be removed
    // - c: the character to be removed
    public static void removeChar(char[] s, char c) {
        // Initialize a pointer j to keep track of the 
      // position where characters are being moved
        int j = 0;
        // Loop through the character array
        for (int i = 0; i < s.length; i++) {
            // If the current character is 
           // not the one to be removed
            if (s[i] != c) {
                // Move the character to the 
               // position indicated by j
                s[j++] = s[i];
            }
        }
        // Fill the remaining positions with null characters ('\0')
        while (j < s.length) {
            s[j++] = '\0';
        }
    }

    public static void main(String[] args) {
        // Input string as a character array
        char[] s = "geeksforgeeks".toCharArray();
        // Remove character 'g' from the string
        removeChar(s, 'g');
        // Print the modified string
        System.out.println(s);
    }
}
//This code is added By prachi
Python 
# Python program to remove a particular character
# from a string.

def removeChar(s, c):
    # Initialize variables
    n = len(s)
    j = 0
    
    # Iterate through each character of the string
    for i in range(n):
        # If the character is not equal to 
        # the target character, keep it
        if s[i] != c:
            s[j] = s[i]
            j += 1
    
    # Add null character at the end of the modified string
    s = s[:j]
    
    return s

if __name__ == "__main__":
    s = "geeksforgeeks"
# Convert string to list of characters for modification
    s = list(s)  
    s = removeChar(s, 'g')
# Convert list of characters back to string for printing
    print(''.join(s))  
#this code is contributed by Adarsh .
JavaScript 
// JavaScript program for the above approach

// Function to remove a particular character from a character array
// Parameters:
// - s: the character array from which the character will be removed
// - c: the character to be removed
function removeChar(s, c) {
    // Initialize a pointer j to keep track of the position where characters are being moved
    let j = 0;
    // Loop through the character array
    for (let i = 0; i < s.length; i++) {
        // If the current character is not the one to be removed
        if (s[i] !== c) {
            // Move the character to the position indicated by j
            s[j++] = s[i];
        }
    }
    // Fill the remaining positions with null characters ('\0')
    while (j < s.length) {
        s[j++] = '\0';
    }
}

// Input string as a character array
let s = "geeksforgeeks".split('');
// Remove character 'g' from the string
removeChar(s, 'g');
// Print the modified string
console.log(s.join(''));

// This code is contributed by Susobhan Akhuli

Output
eeksforeeks

Concatenating strings (combining multiple strings into one).

To concatenate any String to a String, we need:

  • A string that is to appended with the string (say “ch”)

Below is the implementation of the above approach:

C++ 
// C++ Program for string
// concatenation using '+' operator
#include <iostream>
using namespace std;

// Driver code
int main()
{
    string init("this is init");
    string add(" added now");

    // Appending the string.
    init = init + add;

    cout << init << endl;
    return 0;
}
C 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    char init[] = "this is init";
    char add[] = " added now";
    char* result = (char*)malloc(strlen(init) + strlen(add) + 1);

    strcpy(result, init);
    strcat(result, add);

    printf("%s\n", result);

    free(result);
    return 0;
}
Java 
public class Main {
    public static void main(String[] args) {
        String init = "this is init";
        String add = " added now";

        // Appending the string.
        init = init + add;

        System.out.println(init);
    }
}

Output
this is init added now

Finding the length/size of a string

To find the length of the String, we need:

  • A string for which the length/size is to be determined (say “str”)

Below is the implementation of the above approach:

C++ 
// C++ program to find length
// of a string
#include <iostream>
#include <string.h>
using namespace std;

// Driver code
int main()
{
    // String obj
    string str = "GeeksforGeeks";

    // size of string object using size() method
    cout << str.size() << endl;

    return 0;
}
C 
#include <stdio.h>
#include <string.h>

int main() {
    // String
    char str[] = "GeeksforGeeks";
    
    // Length of string using strlen() function
    int length = strlen(str);
    
    printf("%d\n", length);
    
    return 0;
}

Output
13

Comparing Strings for Equality

To compare strings, Define a function to compare values with the following conditions :

  1. if (string1 != string2) it returns a False.
  2. if both the strings are equal lexicographically (string1 == string2), it returns True.

Below is the implementation of the above approach:

C++ 
#include <iostream>
using namespace std;

bool stringCompare(const string& str1, const string& str2) {
    int l1 = str1.length();
    int l2 = str2.length();
    int lmin = min(l1, l2);

    for (int i = 0; i < lmin; i++) {
        int str1_ch = static_cast<int>(str1[i]);
        int str2_ch = static_cast<int>(str2[i]);

        if (str1_ch != str2_ch) {
            return false;
        }
    }

    if (l1 != l2) {
        return false;
    } else {
        return true;
    }
}

int main() {
    string string1 = "Geeksforgeeks";
    string string2 = "Practice";
    string string3 = "Geeks";
    string string4 = "Geeks";

    cout << "Comparing " << string1 << " and " << string2 << " : " 
         << stringCompare(string1, string2) << endl;
    cout << "Comparing " << string3 << " and " << string4 << " : " 
         << stringCompare(string3, string4) << endl;
    cout << "Comparing " << string1 << " and " << string4 << " : " 
         << stringCompare(string1, string4) << endl;

    return 0;
}
C 
#include <stdio.h>
#include <stdbool.h>
#include <string.h>

// This function compares two strings lexicographically
bool stringCompare(const char* str1, const char* str2) {
    int l1 = strlen(str1);
    int l2 = strlen(str2);
    int lmin = (l1 < l2) ? l1 : l2;

    for (int i = 0; i < lmin; i++) {
        int str1_ch = (int)str1[i];
        int str2_ch = (int)str2[i];

        if (str1_ch != str2_ch) {
            return false;
        }
    }

    // Edge case for strings with different lengths
    if (l1 != l2) {
        return false;
    }

    // If none of the above conditions is true,
    // it implies both the strings are equal
    return true;
}

// Driver function to test the above program
int main() {
    const char* string1 = "Geeksforgeeks";
    const char* string2 = "Practice";
    const char* string3 = "Geeks";
    const char* string4 = "Geeks";

    // Comparing string1 and string2
    printf("Comparing %s and %s: %s\n", string1, string2, 
            stringCompare(string1, string2) ? "true" : "false");

    // Comparing string3 and string4
    printf("Comparing %s and %s: %s\n", 
            string3, string4, stringCompare(string3, string4) ? 
            "true" : "false");

    // Comparing string1 and string4
    printf("Comparing %s and %s: %s\n", 
            string1, string4, stringCompare(string1, string4) ? 
            "true" : "false");

    return 0;
}
Java 
// Java program to Compare two strings
// lexicographically
public class GFG {

    // This method compares two strings
    // lexicographically without using
    // library functions
    public static Boolean stringCompare(String str1,
                                        String str2)
    {

        int l1 = str1.length();
        int l2 = str2.length();
        int lmin = Math.min(l1, l2);

        for (int i = 0; i < lmin; i++) {
            int str1_ch = (int)str1.charAt(i);
            int str2_ch = (int)str2.charAt(i);

            if (str1_ch != str2_ch) {
                return false;
            }
        }

        // Edge case for strings like
        // String 1="Geeks" and String 2="Geeksforgeeks"
        if (l1 != l2) {
            return false;
        }

        // If none of the above conditions is true,
        // it implies both the strings are equal
        else {
            return true;
        }
    }

    // Driver function to test the above program
    public static void main(String args[])
    {
        String string1 = new String("Geeksforgeeks");
        String string2 = new String("Practice");
        String string3 = new String("Geeks");
        String string4 = new String("Geeks");

        // Comparing for String 1 < String 2
        System.out.println(
            "Comparing " + string1 + " and " + string2
            + " : " + stringCompare(string1, string2));

        // Comparing for String 3 = String 4
        System.out.println(
            "Comparing " + string3 + " and " + string4
            + " : " + stringCompare(string3, string4));

        // Comparing for String 1 > String 4
        System.out.println(
            "Comparing " + string1 + " and " + string4
            + " : " + stringCompare(string1, string4));
    }
}
Python 
def string_compare(str1, str2):
    l1 = len(str1)
    l2 = len(str2)
    lmin = min(l1, l2)

    for i in range(lmin):
        str1_ch = ord(str1[i])
        str2_ch = ord(str2[i])

        if str1_ch != str2_ch:
            return 0

    if l1 != l2:
        return 0
    else:
        return 1

string1 = "Geeksforgeeks"
string2 = "Practice"
string3 = "Geeks"
string4 = "Geeks"

print("Comparing", string1, "and", string2, ":", 
       string_compare(string1, string2))
print("Comparing", string3, "and", string4, ":", 
       string_compare(string3, string4))
print("Comparing", string1, "and", string4, ":", 
       string_compare(string1, string4))
#this code is contributed by Adarsh.
JavaScript 
// Function to compare two strings
function stringCompare(str1, str2) {
    const l1 = str1.length;
    const l2 = str2.length;
    const lmin = Math.min(l1, l2);

    // Iterate over the strings and compare characters
    for (let i = 0; i < lmin; i++) {
        const str1_ch = str1.charCodeAt(i);
        const str2_ch = str2.charCodeAt(i);

        if (str1_ch !== str2_ch) {
            return 0; // If characters don't match, return 0
        }
    }

    // If lengths are not equal, return 0
    if (l1 !== l2) {
        return 0;
    } else {
        return 1; // Otherwise, return 1
    }
}

const string1 = "Geeksforgeeks";
const string2 = "Practice";
const string3 = "Geeks";
const string4 = "Geeks";

console.log("Comparing", string1, "and", 
             string2, ":", stringCompare(string1, string2));
console.log("Comparing", string3, "and", 
             string4, ":", stringCompare(string3, string4));
console.log("Comparing", string1, "and", 
             string4, ":", stringCompare(string1, string4));
// This code is contributed by Utkarsh.

Output
Comparing Geeksforgeeks and Practice : 0
Comparing Geeks and Geeks : 1
Comparing Geeksforgeeks and Geeks : 0


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