Iterator Types: begin(), end(), rbegin(), rend(), cbegin()

Intermediate12 min read•Updated: 2026-10-22

🧭 Iterator Types: begin(), end(), rbegin(), and cbegin()

Introduction

An iterator is an object that adheres to pointer semantics (*, ++, ==), enabling traversal across different container types using a uniform interface.

🗺️ Visualizing Container Boundaries

[ Element 0 ]  [ Element 1 ]  [ Element 2 ]  [ Element 3 ]
     ▲                                              ▲
     │                                              │
  begin()                                         end() (Past-the-end element!)

Notice that end() does NOT point to the last element; it points to the hypothetical element immediately following the last element.

🔄 The 4 Iterator Access Modes

1#include <iostream>
2#include <vector>
3 
4int main() {
  std::vector<int> numbers = {10, 20, 30, 40, 50};
6 
  // 1. Forward Traversal: begin() to end()
  std::cout << "Forward: ";
  for (auto it = numbers.begin(); it != numbers.end(); ++it) {
      std::cout << *it << " ";
  }
  std::cout << "\n";
13 
  // 2. Reverse Traversal: rbegin() to rend()
  std::cout << "Reverse: ";
  for (auto rit = numbers.rbegin(); rit != numbers.rend(); ++rit) {
      std::cout << *rit << " "; // 50 40 30 20 10
  }
  std::cout << "\n";
20 
  // 3. Const Iterators: cbegin() to cend() (Read-only protection)
  std::cout << "Const:   ";
  for (auto cit = numbers.cbegin(); cit != numbers.cend(); ++cit) {
      // *cit = 99; // 💥 Compiler halts: read-only location
      std::cout << *cit << " ";
  }
  std::cout << "\n";
28 
  return 0;
30}

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Unordered Containers: std::unordered_map and std::unordered_set (Hash Tables)	Sorting and Searching: std::sort, std::stable_sort, std::binary_search

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Sorting and Searching: std::sort, std::stable_sort, std::binary_search

Iterator Types: begin(), end(), rbegin(), rend(), cbegin()

Intermediate12 min read•Updated: 2026-10-22

Study Materials

🧭 Iterator Types: begin(), end(), rbegin(), and cbegin()

Introduction

An iterator is an object that adheres to pointer semantics (*, ++, ==), enabling traversal across different container types using a uniform interface.

🗺️ Visualizing Container Boundaries

[ Element 0 ]  [ Element 1 ]  [ Element 2 ]  [ Element 3 ]
     ▲                                              ▲
     │                                              │
  begin()                                         end() (Past-the-end element!)

Notice that end() does NOT point to the last element; it points to the hypothetical element immediately following the last element.

🔄 The 4 Iterator Access Modes

1#include <iostream>
2#include <vector>
3 
4int main() {
  std::vector<int> numbers = {10, 20, 30, 40, 50};
6 
  // 1. Forward Traversal: begin() to end()
  std::cout << "Forward: ";
  for (auto it = numbers.begin(); it != numbers.end(); ++it) {
      std::cout << *it << " ";
  }
  std::cout << "\n";
13 
  // 2. Reverse Traversal: rbegin() to rend()
  std::cout << "Reverse: ";
  for (auto rit = numbers.rbegin(); rit != numbers.rend(); ++rit) {
      std::cout << *rit << " "; // 50 40 30 20 10
  }
  std::cout << "\n";
20 
  // 3. Const Iterators: cbegin() to cend() (Read-only protection)
  std::cout << "Const:   ";
  for (auto cit = numbers.cbegin(); cit != numbers.cend(); ++cit) {
      // *cit = 99; // 💥 Compiler halts: read-only location
      std::cout << *cit << " ";
  }
  std::cout << "\n";
28 
  return 0;
30}

Next Lesson

Sorting and Searching: std::sort, std::stable_sort, std::binary_search

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Unordered Containers: std::unordered_map and std::unordered_set (Hash Tables)	Sorting and Searching: std::sort, std::stable_sort, std::binary_search

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next