My code passed!! But it shouldn't pass for string: "ra4d5ar".

#include <bits/stdc++.h>
using namespace std;

class Solution {
public:
bool checkPalindrome(string s) {
        queue<char> q; string str{};
        for(char c: s){
            if(c>='a' && c<='z'){
                str += c;
            }
            else if(c>='A' && c<='Z'){
                str += (c+32);
            }
        }
        for(char c : str){
            q.push(c);
        }

        for(int i=str.length()-1; i>0; i--){
            char ch1 = str[i];
            char ch2 = q.front();
            if(ch1 != ch2){
                return false;
            }
            q.pop();
        }
        return true;
    }
};