C++ - Strings: Access

Overview

Estimated time: 15–20 minutes

Read and modify characters by index, and iterate over strings safely.

Learning Objectives

• Use operator[] vs at() and know the bounds-checking difference.
• Iterate with range-for and iterators.

Prerequisites

• C++ - Strings: Length

Examples

#include <string>
#include <iostream>
int main(){
  std::string s = "hello";
  s[0] = 'H';
  try { s.at(10) = '!'; }
  catch(const std::out_of_range&){ std::cout << "OOR"; }
  for(char ch : s) std::cout << ch;
}

Common Pitfalls

• operator[] has undefined behavior on out-of-range access; prefer at() when safety matters.