validPalindromeleetcode.cpp

class Solution {
    private: bool isValid(char ch){
        if((ch >= 'a'&& ch <= 'z') || (ch>='A' && ch <= 'Z') || (ch >= '0'&& ch <= '9')){
            return 1;
        }
        
        return 0;
    }
    char toLowerCase(char ch){
        if((ch >='a' && ch<= 'z') || (ch >='0' && ch<= '9')){
            return ch;
        }else{
            char temp = ch -'A' + 'a';
            return temp;
        }
    }
    
    bool checkPalindrome(string s){
        int start = 0;
        int end = s.length()-1;
        
        while(start<=end){
            if(s[start] != s[end]){
                return 0;
            }else{
                start++;
                end--;
            }
        }
        return 1;
    }
    
public:
    bool isPalindrome(string s) {
        string temp = "";
        for(int i = 0 ; i< s.length() ; i++){
            if(isValid(s[i])){
                temp.push_back(s[i]);
            }
        }
        
        //lowercase
        for(int j =0 ; j< temp.length() ; j++){
            temp[j] = toLowerCase(temp[j]);
        }
        
        return checkPalindrome(temp);
    }
};