Check if a string is a palindrome in C++

Check if a string is a palindrome in C++

One of the most common exercises when learning to program with strings is to check whether a string is a palindrome or not. First of all, let's define what a palindrome is: it is a string that reads the same backward as forward. For a more accurate description, I recommend Palindroma Definition.

Now that we know what a palindrome is, all we have to do is turn our idea into code.

Given an input string, check if it's a palindrome.

First, let's define a function that returns true or false depending on whether the string is a palindrome or not.

bool isPalindroma(string str){
  for(int i = 0, _i = str.length()-1; i< str.length() / 2; i++){
    if(str[i] != str[_i--])
      return false;
  }
  return true;
}

The reasoning here is very simple. I iterate through the string from index 0 to index str.length() / 2, which is the middle of the string, and ask a simple question: is the element at position i different from the element at position str.length() - 1 - i? If this condition is true, the string is not a palindrome, so I return false. Otherwise, I continue with the loop until I reach the middle of the string. If the loop completes, the string is a palindrome, so I return true.

Now all we have to do is use it in our main function.

int main(){

  string str = "";
  cin >> str;

  string isP = isPalindrome(str) ? "is a palindrome " : "is not a palindrome ";
  cout << str << isP;
  return 0; 
}

P.S. Don t forget to include string, iostream, and the std namespace at the beginning of the file.

#include < iostream >
#include < string >