Replace a sub-string in a string in C++

Understanding String Manipulation

Replacing a sub-string in a string means finding a specific sequence of characters and replacing it with another sequence.

We will explore three different methods to achieve this in C++.

Method 1: Using Loop

This method iterates through the string and replaces occurrences of the sub-string.

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

void replaceSubstring(string &str, const string &oldWord, const string &newWord) {
    size_t pos = 0;
    while ((pos = str.find(oldWord, pos)) != string::npos) {
        str.replace(pos, oldWord.length(), newWord);
        pos += newWord.length();
    }
}

int main() {
    string str = "Hello World!";
    replaceSubstring(str, "World", "C++");
    cout << "Modified String: " << str;
    return 0;
}
            

Method 2: Using Recursion

This method replaces the sub-string recursively.

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

void replaceRecursive(string &str, const string &oldWord, const string &newWord) {
    size_t pos = str.find(oldWord);
    if (pos == string::npos) return;
    str.replace(pos, oldWord.length(), newWord);
    replaceRecursive(str, oldWord, newWord);
}

int main() {
    string str = "I love programming";
    replaceRecursive(str, "love", "enjoy");
    cout << "Modified String: " << str;
    return 0;
}
            

Method 3: Using String Functions

This method uses C++'s built-in find() and replace() functions.

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

void replaceUsingFunctions(string &str, const string &oldWord, const string &newWord) {
    size_t pos = str.find(oldWord);
    if (pos != string::npos) {
        str.replace(pos, oldWord.length(), newWord);
    }
}

int main() {
    string str = "Replace old text";
    replaceUsingFunctions(str, "old", "new");
    cout << "Modified String: " << str;
    return 0;
}