How Can I Efficiently Replace Substrings in C ?

Replacing a String Fragment with a New String

Replacing a specific portion of a string with an alternative string is a common task in programming. In C , the standard libraries provide a convenient solution for achieving this.

To replace a substring, you can leverage the find() function to locate the starting position of the target substring within the original string. Subsequently, you can utilize the replace() function to substitute the target substring with the desired replacement string.

The following code snippet demonstrates the process:

bool replace(std::string& str, const std::string& from, const std::string& to) {
    size_t start_pos = str.find(from);
    if(start_pos == std::string::npos)
        return false;
    str.replace(start_pos, from.length(), to);
    return true;
}

std::string string("hello $name");
replace(string, "$name", "Somename");

By employing this approach, you can effectively modify a portion of a string as required.

Handling Multiple Replacements

In certain scenarios, you may need to replace multiple instances of a particular substring within a string. To address this, you can consider the replaceAll() function, which would resemble the following:

void replaceAll(std::string& str, const std::string& from, const std::string& to) {
    if(from.empty())
        return;
    size_t start_pos = 0;
    while((start_pos = str.find(from, start_pos)) != std::string::npos) {
        str.replace(start_pos, from.length(), to);
        start_pos += to.length(); // In case 'to' contains 'from', like replacing 'x' with 'yx'
    }
}

This function iterates through the string, locating and replacing all occurrences of the specified substring with the provided replacement string.

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