How to Efficiently Replace Substrings in C Strings?

Replace Part of a String with Another String

Replacing a substring within a string is a common task in programming, and C provides several ways to do it. One approach is to use the standard C library functions find and replace.

Using find and replace

The find function takes a string and a substring as arguments, and it returns the position of the substring within the string. If the substring is not found, find returns string::npos. To replace a substring with another substring, you can use the replace function. The replace function takes a string, a substring to be replaced, and a new substring to replace it with. Here's an example:

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");

Using replaceAll

If you need to replace all occurrences of a substring with another substring, you can use a function called replaceAll. Here's an example implementation of replaceAll:

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'
    }
}

Both replace and replaceAll are efficient and straightforward to use. They are suitable for replacing substrings within strings in a variety of applications.

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