Find The Position Of The Last Occurrence Of A Substring In A String In C++

Finding the position of each character or a particular sequence of characters, also known as a substring, in a string is a common task when handling strings in C++. In this article, we are going to write a simple code that allows developers to find the position of the last occurrence of a substring in a string.

Code snippet: Finding the Last Occurrence of a Substring

Here is the C++ code snippet for finding the last occurrence of a substring in a string.

#include <iostream>
#include <string>

int main() {
  std::string str = "Hello world, welcome to the world of C++.";
  std::string substring = "world";

 size_t pos = str.rfind(substring);

  if(pos != std::string::npos) {
    std::cout << "Last occurrence is at: " << pos << std::endl;
  } else {
    std::cout << "Substring not found." << std::endl;
  }

  return 0;
}

Code Explanation for Finding the Last Occurrence of a Substring

To begin, we include the necessary libraries, iostream for input-output stream and string for string operations.

#include <iostream>
#include <string>

Next, in the main function, we define our sample string str and the substring we want to find the last occurrence of.

std::string str = "Hello world, welcome to the world of C++.";
std::string substring = "world";

We then use the rfind() function provided by the C++ standard string class. This function returns the highest index where the substring is found. If the substring is not found, it returns std::string::npos.

size_t pos = str.rfind(substring);

Finally, we check whether a position has been found. If pos is not equal to std::string::npos, this means a match for the substring was found, so we print out the position. Otherwise, we inform the user that the substring was not found.

if(pos != std::string::npos) {
    std::cout << "Last occurrence is at: " << pos << std::endl;
} else {
    std::cout << "Substring not found." << std::endl;
}

By running the program with different strings and substrings, you can clearly understand how it works. We can adjust the code depending on the specific requirements of your tasks.