C++ Tutorial · Control Flow and Functions · Lesson 8 of 21

C++ Conditions and Loops

if, switch, for, range-based for, while and do-while.

Conditions

Example 1

#include <iostream>

int main() {
    int temp = 31;
    if (temp > 30) {
        std::cout << "Hot\n";
    } else if (temp > 20) {
        std::cout << "Warm\n";
    } else {
        std::cout << "Cold\n";
    }
    char grade = 'B';
    switch (grade) {
        case 'A': std::cout << "Excellent\n"; break;
        case 'B':
        case 'C': std::cout << "Good\n"; break;
        default: std::cout << "Keep going\n";
    }
    if (int n = temp / 10; n == 3) std::cout << "if with initializer: " << n << '\n';
}

Output

Hot
Good
if with initializer: 3

Run this on your computer — see “Get Started” for setup.

Loops

The range-based for loop is the modern way to visit every element. Use const auto& to avoid copying:

Example 2

#include <iostream>
#include <string>
#include <vector>

int main() {
    for (int i = 0; i < 3; ++i) std::cout << i << ' ';
    std::cout << '\n';
    std::vector<std::string> langs{"C++", "Rust", "Zig"};
    for (const auto& lang : langs) std::cout << lang << ' ';
    std::cout << '\n';
    int n = 1;
    while (n < 100) n *= 3;
    std::cout << n << '\n';
    for (int i = 1; i <= 10; ++i) {
        if (i % 2 == 0) continue;
        if (i > 7) break;
        std::cout << i << ' ';
    }
    std::cout << '\n';
}

Output

0 1 2 
C++ Rust Zig 
243
1 3 5 7

Run this on your computer — see “Get Started” for setup.

Test yourself

Why write for (const auto& x : items)?

To modify each element
To read each element without copying it
To loop backwards
It's required syntax

Show answer

Answer: To read each element without copying it