How to Remove Specific Characters from Strings in C ?

Removing Specific Characters from Strings in C

Many applications require manipulating user inputs, and removing unwanted characters from strings is a common task. This article addresses how to efficiently achieve this task in C .

Problem Statement:

Consider a scenario where a user enters a phone number:

cout << "Enter phone number: ";
string phone;
cin >> phone;

The raw input might contain additional characters like parentheses and dashes: "(555) 555-5555". The goal is to remove these characters to obtain a clean numeric string.

Solution:

The C Standard Library provides a convenient method to achieve this. The std::remove algorithm iterates through a string and removes instances of a specified character. However, it doesn't directly modify the original string.

string str("(555) 555-5555");

char charsToRemove[] = "()-";  // Characters to be removed

for (unsigned int i = 0; i < strlen(charsToRemove); ++i) {
  str.erase(std::remove(str.begin(), str.end(), charsToRemove[i]), str.end());
}

// Output: 555 5555555
cout << str << endl;

Function-Based Approach:

For ease of use, you can define a function that takes a string and a character array as inputs and performs the character removal:

void removeCharsFromString(string &str, char* charsToRemove) {
  for (unsigned int i = 0; i < strlen(charsToRemove); ++i) {
    str.erase(std::remove(str.begin(), str.end(), charsToRemove[i]), str.end());
  }
}

This function can then be called with the desired strings to remove specific characters. For example:

string phone = "(555) 555-5555";
removeCharsFromString(phone, "()-" );

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