Strings in C++

C++ mein strings kaafi important topic hai jab aapko characters ya text handle karna hota hai. C++ do tarah se string ko handle karta hai:

1. Character arrays (C-style strings)
2. string class (C++ STL)

1. Character Array (C-style Strings)

Sabse pehle traditional C-style strings dekhte hain jisme characters ek array ke form mein store hote hain, aur string ka end null character se hota hai.

Declaration & Initialization

char name[] = {'B', 'E', 'Y', 'O', 'N', 'D', ' ', 'M', 'A', 'N'};

Ya phir shortcut:

char name[] = "Beyond Man";

"Beyond Man" ke andar last mein automatically \0 add hota hai.

2. Input and Output in Character Arrays

char name[20];
cin >> name;         // space tak ka input lega
cout << name;

Limitation: cin sirf space tak ka text read karta hai. Poora sentence lena ho toh cin.getline() use karte hain.

cin.getline(name, 20);

 3. String Functions (C-style)

strlen(str);    // length
strcpy(dest, src);  // copy
strcmp(str1, str2); // compare
strcat(str1, str2); // concatenate

4. C++ String Class (STL)

Modern C++ mein string class use karna jyada easy aur safe hota hai. Ye class #include <string> se aati hai.

Declaration:

string name = "Beyond Man";

Input & Output:

string fullName;
getline(cin, fullName);  // entire line input
cout << fullName;

5. Common Operations on Strings

string a = "Hello";
string b = "World";

string c = a + " " + b;      // Concatenation
cout << c;                   // Output: Hello World

cout << a.length();          // Length of string

cout << a[1];                // Access character: 'e'

 6. Useful String Functions (C++)

Function Purpose

s.length() Length of string

s.empty() Check if string is empty

s.append("xyz") Add to end

s.substr(0, 5) Substring from index 0 of length 5

s.find("lo") Find substring, returns index

s.compare(s2) Compare two strings

s.erase(0, 2) Erase part of string

7. Example Programs

Program 1: Reverse a String

#include <iostream>
#include <algorithm>  // Required for reverse()
#include <string>     // Required for using string class
using namespace std;

int main() {
    string str = "Beyond Man";
    // Reversing the string using reverse() from <algorithm>
    reverse(str.begin(), str.end());    
    // Output the reversed string
    cout << "Reversed string: " << str << endl;
    return 0;
}

Output:

Reversed string: naM dnoyeB

Program 2: Check if a String is Palindrome

#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

int main() {
    string str;
    cout << "Enter a string: ";
    cin >> str;  // Takes input without spaces

    // Create a copy and reverse it
    string rev = str;
    reverse(rev.begin(), rev.end());

    if (str == rev) {
        cout << "Palindrome" << endl;
    } else {
        cout << "Not Palindrome" << endl;
    }

    return 0;
}

Output:

Enter a string: madam

Palindrome

Program 3: Count Vowels in a String

#include <iostream>
#include <string>
using namespace std;

int main() {
    string s;
    cout << "Enter a string: ";
    getline(cin, s);  // Accepts the whole line including spaces

    int count = 0;
    for (char c : s) {
        c = tolower(c);  // Convert character to lowercase for comparison
        if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u') {
            count++;
        }
    }

    cout << "Number of vowels: " << count << endl;

    return 0;
}

Output:

Enter a string: Hello World

Number of vowels: 3

Practice Questions

1. Ek string lo aur count karo kitne capital letters hain.
2. Ek string lo aur har word ko nayi line mein print karo.
3. Do strings input lo aur check karo kya wo anagrams hain.
4. Ek string input lo aur vowel ko * se replace karo.