C++ Recursion: Calculating the sum of even and odd numbers in a range

C++ Recursion: Exercise-14 with Solution

Write a C++ program to implement a recursive function to calculate the sum of even and odd numbers in a given range.

Sample Solution:

C Code:

// Recursive function to calculate the sum of even and odd numbers in a range
#include <iostream>

// Recursive function to calculate the sum of even and odd numbers within a given range
void calculate_even_odd_Sum(int start, int end, int & evenSum, int & oddSum) {
  // Base case: If start becomes greater than end, stop the recursion
  if (start > end)
    return;

  // Recursive case: add the current number to the appropriate sum
  if (start % 2 == 0)
    evenSum += start; // Add the current number to the even sum
  else
    oddSum += start; // Add the current number to the odd sum

  // Recursively call the function with the next number in the range
  calculate_even_odd_Sum(start + 1, end, evenSum, oddSum);
}

int main() {
  int start, end;
  std::cout << "Input the starting number: ";
  std::cin >> start;
  std::cout << "Input the ending number: ";
  std::cin >> end;

  int even_Sum = 0;
  int odd_Sum = 0;

  // Calculate the sum of even and odd numbers using recursion
  calculate_even_odd_Sum(start, end, even_Sum, odd_Sum);

  std::cout << "Sum of even numbers: " << even_Sum << std::endl;
  std::cout << "Sum of odd numbers: " << odd_Sum << std::endl;

  return 0;
}

Sample Output:

Input the starting number: 1
Input the ending number: 10
Sum of even numbers: 30
Sum of odd numbers: 25

Explanation:

In the above exercise,

• The "calculate_even_odd_Sum()" function takes the starting number (start), ending number (end), and two integer references (evenSum and oddSum) as parameters.
• It uses recursion to calculate the sum of even and odd numbers in the given range.
• The base case is when the start is greater than the end, in which case the function stops recursion.
• In the recursive case, the function checks if the start number is even or odd using the modulo operator (%).
• If it's even, it adds it to the even_Sum variable; otherwise, it adds it to the odd_Sum variable.
• Then, it recursively calls the function with the next number in the range (start + 1). The recursive calls continue until the base case is reached.

The "main()" function prompts the user to input the starting and ending numbers. It initializes the even_Sum and odd_Sum variables, calls the "calculate_even_odd_Sum()" function to calculate the sums using recursion, and then displays the sums of even and odd numbers on the console.

Flowchart:

CPP Code Editor:

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