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std::string::replace() in C++

Last Updated : 29 May, 2026

The std::string::replace() function in C++ is used to replace characters or substrings inside a string. It is a member function of the std::string class and provides multiple overloads for replacing text using indexes or iterators.

  • It can replace characters, substrings, or ranges of characters.
  • It supports replacement using indexes as well as iterators.

Output
Hello C++

Explanation:

  • Replacement starts from index 6.
  • 5 characters (World) are replaced with "C++".

Common Syntax of string::replace()

SyntaxDescription
str.replace(pos, count, n, ch)Replaces count characters starting from pos with n copies of character ch.
str.replace(pos, count, str2)Replaces characters with another string.
str.replace(pos1, count, str2, pos2, len)Replaces characters with a substring of another string.
str.replace(first, last, n, ch)Replaces iterator range with repeated characters.
str.replace(first, last, str2)Replaces iterator range with another string.
str.replace(first, last, str2_first, str2_last)Replaces iterator range with another iterator range.

Replace Using Indexes

n index-based replacement, positions are specified using integer indexes.

Replace with Repeated Character

The string::replace() method can be used to replace the multiple characters with single repeated character.

Syntax

str1.replace(pos, n, m, c)

Parameters

  • str1: String in which we have to replace the multiple characters.
  • pos: Index to the position in str1 where we have to start replacing the characters.
  • n: Number of characters which we have to replace.
  • m: Number of times we have to repeat the single character.
  • c: Character by which we have to replace.

Return Value: It returns the original string after replacing the multiple characters with single repeated character.


Output
!!! World

Replace with Another String

Syntax

str1.replace(pos, n, str2)

Parameters

  • str1: String in which we have to replace.
  • pos: Index to the position in str1 where we have to start replacing the characters.
  • n: Number of characters which we have to replace.
  • str2: String by which we have to replace the characters.

Return Value: It returns the original string after replacing the multiple characters by another string.


Output
Hello World

Replace with Substring

The string::replace() method can also be used to replace the multiple characters with a part of the given string.

Syntax

str1.replace(pos1, n, str2, pos2,m)

Parameters

  • str1: The string in which we have to replace.
  • pos1: Index to the position in str1 where we have to start replacing the characters.
  • n: Number of characters which we have to replace.
  • str2: String by which we have to replace the characters.
  • pos2: Starting index of substring which we have to replace with multiple characters.
  • m: Numbers of the character in the substring by which we have to replace.

Return Value: It returns the original string after replacing the multiple characters by another substring.


Output
Hello World

Replace Using Iterator

Replace Iterator Range with Repeated Character

The string::replace() method can be used to replace the multiple characters with a single repeated character.

Syntax

str1.replace(first, last, n, c);

Parameters

  • str1: The string in which we have to replace the multiple characters.
  • first: Iterator pointing to the starting position of str1 from where we have to replace the multiple characters.
  • last: Iterator pointing to the position just after the last element up to which we have to replace.
  • n: Number of single repeated character by which we have to replace.
  • c: Character by which we have to replace.

Return Value: It return the original string after replacing the multiple characters with single repeated character.


Output
!!! World

Replace with Another String

The string::replace() method can also be used to replace the multiple characters with a string.

Syntax

str1.replace(first, last, str2)

Parameters

  • str1: The string in which we have to replace the multiple characters.
  • first: Iterator pointing to the starting position of str1 from where we have to replace the multiple characters.
  • last: Iterator pointing to the position just after the last element up to which we have to replace.
  • str2: String by which we have to replace the characters.

Return Value: It return the original string after replacing the multiple characters by another string.


Output
Hello World

Replace with Substring (Iterator Range)

The string::replace() method can also be used to replace the multiple characters with a substring.

Syntax

str1.replace(first, last, str2_first, str2_last)

Parameters

  • str1: The string in which we have to replace the multiple characters.
  • first: Iterator pointing to the starting position of str1 from where we have to replace.
  • last: Iterator pointing to the position just after the last element up to which we have to replace.
  • str2_first: Iterator pointing to the starting position of substring by which we have to replace.
  • str2_last: Iterator pointing to the position just after the last element of the substring.

Return Value: It returns the original string after replacing the multiple characters by another substring.


Output
Hello World
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