Iterate over String

Iterating through each character of a std::string using a range-based for loop is a convenient and efficient way to access and manipulate each character individually.

Basic Usage

The range-based for loop in C++ simplifies the process of iterating through the elements of a container like std::string. Here’s how you can do it:

1#include <iostream>
2#include <string>
3
4int main() {
5  std::string Greeting{"Hello"};
6
7  for (const char& Character : Greeting) {  
8    std::cout << Character << '\n';         
9  }                                         
10}

1H
2e
3l
4l
5o

Modifying Characters

If you need to modify the characters in the string, you can omit the const keyword and use a reference.

1#include <iostream>
2#include <string>
3
4int main() {
5  std::string Greeting{"Hello"};
6
7  for (char& Character : Greeting) {
8    Character = toupper(Character);  
9  }
10
11  std::cout << Greeting;
12}

1HELLO

Accessing Index

If you need the index of each character, use a traditional for loop with the at() method or direct indexing.

1#include <iostream>
2#include <string>
3
4int main() {
5  std::string Greeting{"Hello"};
6
7  for (size_t i = 0; i < Greeting.size(); ++i) {
8    std::cout << "Character at index "
9      << i << " is " << Greeting[i] << '\n';  
10  }
11}

1Character at index 0 is H
2Character at index 1 is e
3Character at index 2 is l
4Character at index 3 is l
5Character at index 4 is o

Considerations

• Read-Only vs Modifiable: Use const for read-only access and omit it for modifying characters.
• Performance: The range-based for loop is efficient and concise for most use cases.

By using the range-based for loop, you can easily and efficiently iterate over each character in a std::string.