Basic String Operations with Implementation
Last Updated :
07 Oct, 2024
In this post, we will look into some of the basic String operations such as:
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:
- A non-empty string (say “s”)
- 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 = s[k];
OR
char ch = s.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 &s, int k)
{
// return the character at Kth index
// in the string str
return s[k];
}
// Driver code
int main()
{
string s("GeeksforGeeks ");
int k = 4;
cout << accessCharByIndex(s, k) << endl;
return 0;
}
#include <stdio.h>
#include <string.h>
// Function to demonstrate accessing character by index
char accessCharByIndex(char* s, int k)
{
// Return the character at the kth index in the string
return s[k];
}
// Driver code
int main()
{
char s[] = "GeeksforGeeks ";
int k = 4;
printf("%c\n", accessCharByIndex(s, k));
return 0;
}
public class GFG {
// Function to demonstrate accessCharByIndex
public static char accessCharByIndex(String s, int k) {
// Return the character at the k-th index in the string s
return s.charAt(k);
}
// Driver code
public static void main(String[] args) {
String s = "GeeksforGeeks ";
int k = 4;
System.out.println(accessCharByIndex(s, k));
}
}
# 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
if __name__ == "__main__":
s = "GeeksforGeeks "
k = 4
print(access_char_by_index(s, k))
using System;
class Program {
// Function to access a character by index
static char AccessCharByIndex(string s, int k)
{
// Return the character at the k-th index
return s[k];
}
static void Main()
{
string s = "GeeksforGeeks ";
int k = 4;
Console.WriteLine(AccessCharByIndex(s, k));
}
}
// Function to demonstrate access by index
function accessCharByIndex(s, k) {
// Return the character at the kth index in the string str
return s[k];
}
// Driver code
let s = "GeeksforGeeks ";
let k = 4;
console.log(accessCharByIndex(s, k));
Inserting Character/String into an String.
To insert any Character/String in a String, we need:
- A character/string that is to be inserted in the string (say “ch”)
- 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 &s, string ch, int k)
{
// Inserts ch at kth index of str
s.insert(k, ch);
cout << "Modified String : " << s << endl;
}
// Driver code
int main()
{
string s("GeeksGeeks ");
string ch = "for";
int k = 5;
cout << "Original String : " << s << endl;
insertDemo(s, ch, k);
return 0;
}
#include <stdio.h>
#include <string.h>
void insertDemo(char* s, const char* ch, int k) {
int len1 = strlen(s);
int len2 = strlen(ch);
// Shift characters to the right to make space for ch
for (int i = len1; i >= k; i--) {
s[i + len2] = s[i];
}
// Insert ch at kth index of str
for (int i = 0; i < len2; i++) {
s[k + i] = ch[i];
}
printf("Modified String: %s\n", s);
}
int main() {
char s[] = "GeeksGeeks ";
char ch[] = "for";
int k = 5;
printf("Original String: %s\n", s);
insertDemo(s, ch, k);
return 0;
}
public class Main {
public static void main(String[] args) {
String s = "GeeksGeeks ";
String ch = "for";
int k = 5;
System.out.println("Original String: " + s);
insertDemo(s, ch, k);
}
// Function to demonstrate insert
public static void insertDemo(String s, String ch, int k) {
// Inserts ch at kth index of str
StringBuilder sb = new StringBuilder(s);
sb.insert(k, ch);
String modifiedString = sb.toString();
System.out.println("Modified String: " + modifiedString);
}
}
# 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__":
s = "GeeksGeeks "
ch_to_insert = "for"
index_to_insert = 5
print("Original String:", s)
insert_demo(s, ch_to_insert, index_to_insert)
using System;
class Program
{
// Function to demonstrate insert
static string InsertDemo(string s, string ch, int k)
{
// Inserts ch at kth index of str
return s.Insert(k, ch);
}
// Driver code
static void Main()
{
string s = "GeeksGeeks ";
string ch = "for";
int k = 5;
Console.WriteLine("Original String: " + s);
string modifiedString = InsertDemo(s, ch, k);
Console.WriteLine("Modified String: " + modifiedString);
}
}
// JavaScript equivalent of the given Java code
// Function to demonstrate insert
function insertDemo(s, ch, k)
{
// Inserts ch at kth index of s
let modifiedString = s.slice(0, k) + ch + s.slice(k);
console.log("Modified String: " + modifiedString);
}
// Call the main function
let s = "GeeksGeeks ";
let ch = "for";
let k = 5;
console.log("Original String: " + s);
insertDemo(s, ch, k);
OutputOriginal String : GeeksGeeks
Modified String : GeeksforGeeks
Modifying character in String
To modify any Character in a String, we need:
- A character that is to replaced in the string (say “ch”)
- 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>
using namespace std;
int main()
{
string s = "Geeks Gor Geeks";
int index = 6;
char ch = 'F';
cout << "Original String = " << s << endl;
s.replace(index, 1, 1, ch);
cout << "Modified String = " << s << endl;
return 0;
}
#include <stdio.h>
#include <string.h>
int main()
{
// Define the string
char s[] = "Geeks Gor Geeks";
// Define the index
int index = 6;
// Define the character
char ch = 'F';
// Print the original string
printf("Original String = %s\n", s);
// Modify the string
s[index] = ch;
// Print the modified string
printf("Modified String = %s\n", s);
return 0;
}
public class GFG {
public static void main(String args[])
{
// Get the String
String s = "Geeks Gor Geeks";
// Get the index
int index = 6;
// Get the character
char ch = 'F';
// Print the original string
System.out.println("Original String = " + s);
s = s.substring(0, index) + ch
+ s.substring(index + 1);
// Print the modified string
System.out.println("Modified String = " + s);
}
}
# Function to replace a character at a specific index in a string
def replace_ch(s, index, ch):
# Convert string to list of characters to allow modification
lst = list(s)
# Replace character at the specified index
lst[index] = ch
# Convert back to string and return
return ''.join(lst)
# Entry point of the program
if __name__ == "__main__":
# Original string
s = "Geeks Gor Geeks"
# Index to replace character
index = 6
# New character
ch = 'F'
# Print original string
print("Original String =", s)
# Replace character at the specified index
s = replace_ch(s, index, ch)
# Print modified string
print("Modified String =", s)
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);
}
}
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
OutputOriginal 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++
#include <iostream>
using namespace std;
void removeChar(string &s, char c)
{
int j = 0;
for (int i = 0; i < s.size(); i++) {
if (s[i] != c) {
// Move other characters
s[j++] = s[i];
}
}
// j is new size of the string
s.resize(j);
}
int main()
{
string s = "geeksforgeeks";
removeChar(s, 'g');
cout << s; // Output the modified string
return 0;
}
#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;
}
public class GfG {
// Function to remove a particular character
// from a StringBuilder
// Parameters:
// - s: the StringBuilder from which
// the character will be removed
// - c: the character to be removed
public static void removeChar(StringBuilder s, char c) {
int j = 0;
// Loop through the StringBuilder
for (int i = 0; i < s.length(); i++) {
// If the current character is not the one to be removed
if (s.charAt(i) != c) {
// Move the character to the position indicated by j
s.setCharAt(j++, s.charAt(i));
}
}
// Delete the remaining characters
s.delete(j, s.length());
}
public static void main(String[] args) {
// Input string as a StringBuilder
StringBuilder s = new StringBuilder("geeksforgeeks");
// Remove character 'g' from the string
removeChar(s, 'g');
// Print the modified string
System.out.println(s);
}
}
def removeChar(s, c):
# Use list comprehension to filter
# out the target character
return ''.join([ch for ch in s if ch != c])
if __name__ == "__main__":
s = "geeksforgeeks"
s = removeChar(s, 'g')
print(s)
// 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
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;
}
#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;
}
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);
}
}
def main():
init = "this is init"
add = " added now"
# Concatenate strings
result = init + add
# Print the result
print(result)
# Call the main function
if __name__ == "__main__":
main()
// Define the main function
function main() {
let init = "this is init";
let add = " added now";
// Appending the string.
init = init + add;
console.log(init);
}
// Call the main function
main();
Outputthis 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;
}
#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;
}
public class Main {
public static void main(String[] args)
{
// String object
String str = "GeeksforGeeks";
// Size of string object using length() method
System.out.println(str.length());
}
}
// This code is contributed by Utkarsh
# Main function
def main():
# String object
str = "GeeksforGeeks"
# Size of string object using len() function
print(len(str))
# Calling the main function
if __name__ == "__main__":
main()
// JavaScript program to find length
// of a string
// String
let str = "GeeksforGeeks";
// size of string using length property
console.log(str.length);
Comparing Strings for Equality
C++
// CPP code perform relational
// operation using compare function
#include <iostream>
using namespace std;
void compareFunction(string &s1, string &s2)
{
// comparing both using inbuilt function
int x = s1.compare(s2);
if (x != 0) {
cout << s1 << " is not equal to "
<< s2 << endl;
if (x > 0)
cout << s1 << " is greater than "
<< s2 << endl;
else
cout << s2 << " is greater than "
<< s1 << endl;
}
else
cout << s1 << " is equal to " << s2 << endl;
}
// Driver Code
int main()
{
string s1("geeks");
string s2("forGeeks");
compareFunction(s1, s2);
string s3("geeks");
string s4("geeks");
compareFunction(s3, s4);
return 0;
}
#include <stdio.h>
#include <string.h>
void compareStrings(char *s1, char *s2) {
// comparing both using inbuilt function
int x = strcmp(s1, s2);
if (x != 0) {
printf("%s is not equal to %s\n", s1, s2);
if (x > 0) {
printf("%s is greater than %s\n", s1, s2);
} else {
printf("%s is greater than %s\n", s2, s1);
}
} else {
printf("%s is equal to %s\n", s1, s2);
}
}
int main() {
compareStrings("geeks", "forGeeks");
compareStrings("geeks", "geeks");
return 0;
}
public class RelationalOps {
public static void compareStrings(String s1, String s2) {
// comparing both using inbuilt function
int x = s1.compareTo(s2);
if (x != 0) {
System.out.println(s1 + " is not equal to " + s2);
if (x > 0) {
System.out.println(s1 + " is greater than " + s2);
} else {
System.out.println(s2 + " is greater than " + s1);
}
} else {
System.out.println(s1 + " is equal to " + s2);
}
}
public static void main(String[] args) {
compareStrings("geeks", "forGeeks");
compareStrings("geeks", "geeks");
}
}
def compare_strings(s1, s2):
# comparing both using inbuilt comparison
if s1 != s2:
print("s1 is not equal to s2")
if s1 > s2:
print("s1 is greater than s2")
else:
print("s2 is greater than s1")
else:
print("s1 is equal to s2")
# Driver code
compare_strings("geeks", "forGeeks")
compare_strings("geeks", "geeks")
function compareStrings(s1, s2) {
// comparing both using inbuilt comparison
if (s1 !== s2) {
console.log(`${s1} is not equal to ${s2}`);
if (s1 > s2) {
console.log(`${s1} is greater than ${s2}`);
} else {
console.log(`${s2} is greater than ${s1}`);
}
} else {
console.log(`${s1} is equal to ${s2}`);
}
}
// Driver code
compareStrings("geeks", "forGeeks");
compareStrings("geeks", "geeks");
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