C++ If Else and Switch

C++ if else statements and switch statements let your program choose what to do based on conditions. They work like in C, with a few modern extras.

if, else if and else

#include <iostream>

int main() {
    int hour = 15;
    if (hour < 12) {
        std::cout << "Good morning\n";
    } else if (hour < 18) {
        std::cout << "Good afternoon\n";
    } else {
        std::cout << "Good evening\n";
    }
}

Good afternoon

Ternary Operator

#include <iostream>
#include <string>

int main() {
    int stock = 0;
    std::string status = stock > 0 ? "In stock" : "Sold out";
    std::cout << status << '\n';
}

Sold out

if with an Initializer

Since C++17 you can declare a variable inside the if itself, keeping its scope small.

#include <iostream>
#include <string>

int main() {
    std::string email = "naeem@example.com";
    if (auto at = email.find('@'); at != std::string::npos) {
        std::cout << "Domain: " << email.substr(at + 1) << '\n';
    }
}

Domain: example.com

The C++ Switch Statement

switch compares an integer, char or enum against constant cases. Remember break, or execution falls through to the next case. Mark intentional fall-through with [[fallthrough]].

#include <iostream>

int main() {
    char op = '*';
    int a = 6, b = 7;
    switch (op) {
        case '+': std::cout << a + b << '\n'; break;
        case '-': std::cout << a - b << '\n'; break;
        case '*': std::cout << a * b << '\n'; break;
        default:  std::cout << "Unknown operator\n";
    }
}

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Frequently asked questions

Can I use strings in a C++ switch?

No. switch only works with integral types and enums. Use if else with == for std::string, or map strings to values with std::unordered_map.

What is [[fallthrough]] in C++?

It is an attribute that tells the compiler and readers that falling into the next case is intentional, silencing the warning.

When should I use switch instead of if else?

Use switch when comparing a single integer, char or enum against many fixed values. Use if else for ranges and complex conditions.