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 insertchar accessCharByIndex(string str, int k){ // return the character at Kth index // in the string str return str[k];}// Driver codeint main(){ string str("neveropen "); int k = 4; cout << accessCharByIndex(str, k) << endl; return 0;} |
C
#include <stdio.h>#include <string.h>// Function to demonstrate accessing character by indexchar accessCharByIndex(char* str, int k){ // Return the character at the kth index in the string return str[k];}// Driver codeint main(){ char str[] = "neveropen "; 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 = "neveropen "; int k = 4; System.out.println(accessCharByIndex(str, k)); }} |
Output
s
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 insertvoid insertDemo(string str, string ch, int k){ // Inserts ch at kth index of str str.insert(k, ch); cout << "Modified String : " << str << endl;}// Driver codeint 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 : neveropen
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[] = "neveropen"; 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[] = "neveropen"; 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 codeint 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 codeint main(){ // String obj string str = "neveropen"; // 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[] = "neveropen"; // 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 :
- 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 = "Geeksforneveropen"; 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 lexicographicallybool 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 programint main() { const char* string1 = "Geeksforneveropen"; 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// lexicographicallypublic 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="Geeksforneveropen" 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("Geeksforneveropen"); 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 Geeksforneveropen and Practice : false Comparing Geeks and Geeks : true Comparing Geeksforneveropen and Geeks : false
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