string erase in C++

The string erase() function is a built-in function of the string class that is used to erase the whole or part of the string, shortening its length. The function provides different ways to delete a portion of a string based on either an index position or a range of characters or delete the whole string.

Example :

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

int main() {
    string str = "Hello, World!";

    // Erase a single character sterting
    // from index 5
    str.erase(5, 1);
    
    cout << str;
    return 0;
}

Hello World!

Syntax

The string erase() function provides 5 different overloads for different purposes:

s.erase()                   // Erases whole string
s.erase(idx)             // Erases all characters after idx
s.erase(idx, k)        // Erases k characters after idx
s.erase(itr)             // Erases character at itr
s.erase(first, last) // Erases character in range [first, last)

Let's look at how to use each overload one by one.

Erase Single Character from Given Position

string erase() function can be used for erasing a single character from the specific position in the string.

Syntax

s.erase(itr)

Parameters

• itr: Iterator to the character you want to erase (note that it is an iterator, not index)

Return Value

• Returns the character now at the position of the removed character.
• If no such character is remaining, returns iterator to the string::end()

Example

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

int main() {
    string s("Hello World!");

    // Deletes character at position 4
    s.erase(s.begin() + 4);

    cout << s;
    return 0;
}

Hell World!

Erase Range of Characters

We can also erase a range of characters from the string using string erase() function.

Syntax

s.erase(first, last)

Parameters

• first: Iterator to the first element in the range.
• last: Iterator to one element after the last element in the range.

Return Value

• Returns the character now at the position of the first removed character.
• If no such character is remaining, returns iterator to the string::end()

Example

#include <bits/stdc++.h>
using namespace std;

int main() {
    string s("Hello World!");

    // Define the range as the word "Hello "
  	auto first = s.begin();
  	auto last = s.begin() + 6;
  	
  	// Remove the range [first, last)
    s.erase(first, last);
  
    cout << s;
    return 0;
}

World!

Erase k Characters After Given Position

The below version erases all the characters after the given index, but we can also limit the number of characters to be deleted using string::erase.

Syntax

s.erase(idx, k)

Parameters

• idx: The position (index) at which character deletion begins.
• k: Number of characters to be erased (including character at idx).

Return Value

• This version returns the current string.

Example

#include <bits/stdc++.h>
using namespace std;

int main() {
    string s("Hello World!");

    // Deletes 5 characters starting from index number 0
    s.erase(0, 5);

    cout << s;
    return 0;
}

 World!

Erase All Characters After Given Position

string erase() function can also be instructed to erase the characters after some given position.

Syntax

s.erase(idx)

Parameters

• idx: The position (index) at which character deletion begins.

Return Value

• This version returns the current string.

Example

#include <bits/stdc++.h>
using namespace std;

int main() {
    string s("Hello World!");
  
	// Deletes the word " World!"
    s.erase(5);
  
    cout << s;
    return 0;
}

Hello

Erase All Characters

The string erase() function is able to delete all the characters of the string effectively clearing it. The length of the string will be reduced to 0.

Syntax

s.erase()

Parameter

• This version takes no parameters.

Return Value

• This version returns the current string.

Example

#include <bits/stdc++.h>
using namespace std;

int main() {
    string s("Hello World!");

    // Erasing string using string::erase()
    s.erase();

    cout << s;
    return 0;
}

Output

(no output)

string erase() vs string clear()

The string clear() is a function used to erase the contents of the string, but it is a lot different from string erase(). Below is the table that lists the major differences between string erase() and string clear().