Palindrome quiz

#include <iostream>
#include <algorithm>

using namespace std;

int main(){
	string str;
	getline(cin, str);

	unsigned int n = str.length();
	transform(str.begin(), str.end(), str.begin(), ::tolower);

	bool palindrome = true;
	for(int i = 0, j = n - 1; i < j; i++, j--){
		while(i < j && (str[i] < 'a' || str[i] > 'z'))
			i++;

		while(j > i && (str[j] < 'a' || str[j] > 'z'))
			j--;

		if(str[i] != str[j]){
			palindrome = false;
			break;
		}
	}

	if(palindrome){
		cout << "YES\n";
	} else {
		cout << "NO\n";
	}

	return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED