C++ Decision Making: If, Else, Else-If Ladders & C++17 Init Statements

Decision-making structures allow a program to evaluate one or more conditions and execute specific blocks of code depending on whether the condition evaluates to true or false.

1. Standard If-Else Statement

#include <iostream>

int main() {
    int marks = 78;

    if (marks >= 90) {
        std::cout << "Grade: A+ (Outstanding)\n";
    } else if (marks >= 75) {
        std::cout << "Grade: A (Distinction)\n";
    } else if (marks >= 50) {
        std::cout << "Grade: B (Pass)\n";
    } else {
        std::cout << "Grade: F (Fail - Try Again)\n";
    }

    return 0;
}

2. Modern C++17 "If with Initializer"

In professional software architecture, limiting variable scope reduces bugs. C++17 introduced local initializers inside the if condition:

#include <iostream>
#include <unordered_map>
#include <string>

int main() {
    std::unordered_map<std::string, int> stock = {{"laptop", 15}, {"phone", 0}};

    // 'item' is created, tested, and destroyed ONLY within this if/else block!
    if (auto item = stock.find("laptop"); item != stock.end() && item->second > 0) {
        std::cout << "Item in stock! Quantity: " << item->second << "\n";
    } else {
        std::cout << "Sorry, out of stock.\n";
    }

    // item is now out of scope - clean and safe!
    return 0;
}