C++ String Exercises: Count number of duplicate characters in a given string

Last update on December 20 2024 12:26:00 (UTC/GMT +8 hours)

Write a C++ program to count the number of duplicate characters in a given string.

Note: Spaces are included and characters are case sensitive

Sample Data:
(“APple”) -> 0
(“Remove all special characters from a given string”) -> 31
(“Total number of unique characters of the said two strings.”) ->36

Sample Solution-1:

C++ Code:

#include <bits/stdc++.h> // Includes all standard libraries

using namespace std; // Using the standard namespace

int test(std::string text) { // Function to count duplicate characters in a string
  int ctr = 0; // Counter to keep track of duplicate characters

  sort(text.begin(), text.end()); // Sorts characters in the string alphabetically

  // Iterate through each character in the string
  for (int i = 0; i < text.size(); i++) {
    if (text[i] == text[i + 1]) { // If the current character is the same as the next one
      ctr = ctr + 1; // Increment the counter for duplicate characters
    }
  }
  return ctr; // Return the count of duplicate characters
}

int main() {
  //string text = "APple";
  //string text = "Remove all special characters from a given string.";
  string text = "Total number of unique characters of the said two strings."; // Declare and initialize a string

  cout << "Original String:\n";
  cout << text; // Output the original string
  cout << "\n\nNumber of duplicate characters in the said string: ";
  cout << test(text) << endl; // Call function test and output the number of duplicate characters in the string
}

Sample Output:

Original String:
Total number of unique characters of the said two strings.

Number of duplicate characters in the said string: 36

Flowchart:

Sample Solution-2:

C++ Code:

#include <bits/stdc++.h> // Includes all standard libraries

using namespace std; // Using the standard namespace

int test(std::string text) { // Function to count duplicate characters in a string
    // Creating a set from the characters in the input string, which automatically filters out duplicates
    std::set<char> set(text.begin(), text.end()); 
    int ctr = text.length() - set.size(); // Calculating the difference to get the count of duplicates
    return ctr; // Return the count of duplicate characters
}

int main() {
    string text = "APple"; // Declare and initialize a string
    //string text = "Remove all special characters from a given string.";
    //string text = "Total number of unique characters of the said two strings.";
    cout << "Original String:\n";
    cout << text; // Output the original string
    cout << "\n\nNumber of duplicate characters in the said string: ";
    cout << test(text) << endl; // Call function test and output the number of duplicate characters in the string
}

Sample Output:

Original String:
APple

Number of duplicate characters in the said string: 0

Flowchart:

C++ Code Editor:

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Previous C++ Exercise: Count the number of unique characters of two strings.