Iterate over characters of a string in C++

This post will discuss how to iterate over the characters of a string in C++.

1. Naive Solution

The idea is to iterate over the characters of a std::string using a simple for-loop and print each character at the current index using the [] operator.

void print(const std::string &s)

{

for (std::string::size_type i = 0; i < s.size(); i++) {

std::cout << s[i] << ' ';

}

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Output:

h e l l o

2. Using range-based for-loop

The recommended approach in C++11 and above is to iterate over the characters of a std::string using a range-based for-loop.

void print(const std::string &s)

{

for (char const &c: s) {

std::cout << c << ' ';

}

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Output:

h e l l o

3. Using Iterators

We can also iterate over the characters of a std::string using iterators. Since the iteration is read-only, we can use std::string::const_iterator returned by std::string::cbegin and std::string::cend.

void print(const std::string &s)

{

for (auto it = s.cbegin() ; it != s.cend(); ++it) {

std::cout << *it << ' ';

}

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Output:

h e l l o

4. Using `std::for_each` function

We can even reduce the complexity by using the std::for_each STL algorithm, which applies a specified function to every element of the input range.

#include <iostream>

#include <algorithm>

void fn(char const &c) {

std::cout << c << ' ';

}

void print(const std::string &s) {

std::for_each(s.begin(), s.end(), fn);

}

int main()

{

std::string s("hello");

print(s);

return 0;

}

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Output:

h e l l o

We can even replace the function call with lambda expressions in C++11. A lambda is a convenient way of defining an inline, anonymous functor at the location, where it is passed as an argument to some function.

void print(const std::string &s)

{

std::for_each(s.begin(), s.end(), [] (char const &c) {

std::cout << c << ' ';

});

}

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Output:

h e l l o

5. Overloading `operator<<`

Finally, we can also overload the operator<< for std::string objects, as shown below:

#include <iostream>

#include <iterator>

std::ostream &operator<< (std::ostream &os, const std::string &s)

{

for (char const &c: s) {

os << c << ' ';

}

return os;

}

int main()

{

std::string s("hello");

std::cout << s;

return 0;

}

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Output:

h e l l o

That's all about iterating over characters of a string in C++.

Iterate over characters of a string in C++

1. Naive Solution

2. Using range-based for-loop

3. Using Iterators

4. Using std::for_each function

5. Overloading operator<<

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4. Using `std::for_each` function

5. Overloading `operator<<`