How to Iterate Through a String in C++

1. Use Range Based Loop to Iterate Through a String in C++
2. Use the for Loop to Iterate Through a String in C++

This article will introduce multiple methods of how to iterate through a string while keeping the index count in C++.

Use Range Based Loop to Iterate Through a String in C++

Modern C++ language style recommends the range based iteration for structures that support it. Meanwhile, the current index can be stored in a separate variable of type size_t that will be incremented each iteration. Note that the increment is specified with the ++ operator at the end of the variable because putting it as a prefix would yield an index that starts with 1. The following example shows only the short part of the program output.

#include <iostream>
#include <string>

using std::cin;
using std::cout;
using std::endl;
using std::string;

int main() {
  string text = "They talk of days for which they sit and wait";

  size_t index = 0;
  for (char c : text) {
    cout << index++ << " - '" << c << "'" << endl;
  }

  return EXIT_SUCCESS;
}

Output:

0 - 'T'
1 - 'h'
2 - 'e'
...
43 - 'i'
44 - 't'

Use the for Loop to Iterate Through a String in C++

It has elegance and power in the conventional for loop, as it offers flexibility when the inner scope involves matrix / multidimensional array operations. It’s also the preferred iteration syntax when using advanced parallelization techniques like the OpenMP standard.

#include <iostream>
#include <string>

using std::cin;
using std::cout;
using std::endl;
using std::string;

int main() {
  string text = "They talk of days for which they sit and wait";

  for (int i = 0; i < text.length(); ++i) {
    cout << i << " - '" << text[i] << "'" << endl;
  }

  return EXIT_SUCCESS;
}

Output:

0 - 'T'
1 - 'h'
2 - 'e'
...
43 - 'i'
44 - 't'

Alternatively, we can access the string’s individual characters with the at() member function.

#include <iostream>
#include <string>

using std::cin;
using std::cout;
using std::endl;
using std::string;

int main() {
  string text = "They talk of days for which they sit and wait";

  for (int i = 0; i < text.length(); ++i) {
    cout << i << " - '" << text.at(i) << "'" << endl;
  }

  return EXIT_SUCCESS;
}

Output:

0 - 'T'
1 - 'h'
2 - 'e'
...
43 - 'i'
44 - 't'