Basic String Operations with Implementation

Namachila 2 days ago

0 0 8 minutes read

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:

A non-empty string (say “str”)
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("zambiatek ");
    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[] = "zambiatek ";
    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 = "zambiatek ";
        int k = 4;
        System.out.println(accessCharByIndex(str, k));
    }
}

Output

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 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);
    }
}

Output

Original String : GeeksGeeks 
Modified String : zambiatek

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>
 
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);
    }
}

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[] = "zambiatek";
    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[] = "zambiatek";
    removeChar(s, 'g');
    printf("%s", s);
    return 0;
}

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;
}

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

Output

Comparing Strings for Equality

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

if (string1 != string2) it returns a False.
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 = "Geeksforzambiatek";
    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 = "Geeksforzambiatek";
    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="Geeksforzambiatek"
        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("Geeksforzambiatek");
        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));
    }
}

Output

Comparing Geeksforzambiatek and Practice : false
Comparing Geeks and Geeks : true
Comparing Geeksforzambiatek and Geeks : false

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