C++ rfind()

The C++ rfind() function returns the position of the last occurrence of a given substring or character within a std::string. The search proceeds from right to left, and the function returns std::string::npos if no match is found.

Syntax

string_object.rfind(val, pos = npos);

Parameters:

• val: A character or string to search for.
• pos (Optional): The position to start searching backward from. Defaults to std::string::npos, meaning the end of the string.

Return value:

Returns the index (zero-based) of the last occurrence of val, or std::string::npos if no match is found.

Example 1

In this example, rfind() locates the last occurrence of a substring:

#include <iostream>
#include <string>

int main() {
  std::string text = "hello world, welcome to the world";

  std::size_t pos = text.rfind("world");
  std::cout << "Last occurrence of 'world': " << pos << "\n";

  return 0;
}

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The output of this code is:

Last occurrence of 'world': 28

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Example 2

In this example, rfind() is used to locate the last occurrence of a character:

#include <iostream>
#include <string>

int main() {
  std::string text = "abracadabra";

  std::size_t pos = text.rfind('a');
  std::cout << "Last 'a' found at index: " << pos << "\n";

  return 0;
}

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The output of this code is:

Last 'a' found at index: 10

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Codebyte Example

In this example, the position of the last occurrence of a character is printed using rfind():

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Frequently Asked Questions

1. What does rfind do in C++?

The rfind() function searches a string from right to left and returns the index of the last occurrence of a character or substring. If the value is not found, it returns std::string::npos. It is useful when the needed match appears multiple times and the last one is required.

2. What does string::find() do in C++?

The find() function searches a string from left to right and returns the index of the first occurrence of a specified character or substring. Like rfind(), it returns std::string::npos when no match exists.

3. What does string() do in C++?

Calling std::string() constructs an empty string object. It represents a dynamic sequence of characters and supports operations such as insertion, erasure, concatenation, comparison, and searching.