Range-Based For Loop with an example
Introduced in C++11, the range-based for loop provides a clean, readable syntax to iterate over elements in containers like arrays, vectors, maps, sets, etc.
It eliminates the need for manual indexing or iterator usage.
🔹 Basic Syntax
for (declaration : container) {
// use declaration
}🔸 Example 1: Loop Over std::vector
#include <vector>
#include <iostream>
int main() {
std::vector<int> nums = {1, 2, 3, 4, 5};
for (int n : nums) {
std::cout << n << " ";
}
// Output: 1 2 3 4 5
}🔸 Example 2: With References (Modify Elements)
for (int& n : nums) {
n *= 2;
}🔹 Without &, you get a copy, and changes won’t affect the original container.
🔸 Example 3: With const Reference (Best for Read-Only)
for (const std::string& s : names) {
std::cout << s << "\n";
}✅ Use const & when:
- You’re only reading
- Container holds large objects (like
std::string,std::vector)
🔸 Example 4: Looping Over Array
int arr[] = {10, 20, 30};
for (int x : arr) {
std::cout << x << "\n";
}C++17 Enhancement: Structured Bindings
🔸 Example 5: Loop Over Map
std::map<std::string, int> ages = {{"Alice", 30}, {"Bob", 25}};
for (const auto& pair : ages) {
std::cout << pair.first << " = " << pair.second << "\n";
}C++17 Enhancement:
for (const auto& [name, age] : ages) {
std::cout << name << " is " << age << "\n";
}