Mastering C++: Loops and Conditional Statements Final Review

Welcome to our final class on C++ loops and conditional statements. This lesson reinforces the concepts of loops (while, do-while, for) and control statements (if, if-else). We will also introduce some advanced topics and illustrate their collective use in problem-solving. Let's proceed, connecting these concepts with practical references for a better understanding.

To start, let's review each type of loop and conditional statement. A while loop iterates until its condition becomes false. A do-while loop ensures at least one execution before evaluating the condition. The for loop is beneficial when we know the exact number of iterations. For conditional statements, if tests a condition and executes statements if the condition is true. The if-else statement enables one block for the true condition and another for the false condition. A switch tests for multiple conditions. These constructs are essential for managing our program's flow.

We often require the combination of loops and conditional statements for complex scenarios. For example, consider a situation where we calculate the sum of the first n natural numbers, but only even numbers are taken into account. Here's how you may do it:

#include <iostream>

int main() {
   int n = 10;
   int sum = 0;
   for (int i = 0; i <= n; ++i) {
       if (i % 2 == 0) { 
           sum += i;
       }
   }
   std::cout << "Sum is " << sum << std::endl; // This outputs: Sum is 30

   return 0;
}

Here, the for loop iterates from 0 to n, checking if the number is even within the if statement. The expression i % 2 evaluates to the remainder when i is divided by 2, commonly used to determine if i is even (remainder 0) or odd (remainder 1).

The break and continue statements finely control loop executions in C++. break exits the current loop abruptly, halting the ongoing execution. In contrast, continue skips the remaining code in the current loop iteration, moving to the next iteration.

#include <iostream>

int main() {
   for (int i = 0; i < 10; ++i) {
       if (i > 5) {
           break; // As soon as i > 5, the loop breaks
       }
       std::cout << i << " "; // Prints: 0 1 2 3 4 5
   }
   for (int i = 0; i < 10; ++i) {
       if (i % 2 == 0) {
           continue; // Skips the iteration when i is even
       }
       std::cout << i << " "; // Prints: 1 3 5 7 9
   }

   return 0;
}