Valid Palindrome.txt

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.

Given a string s, return true if it is a palindrome, or false otherwise.

 

Example 1:

Input: s = "A man, a plan, a canal: Panama"
Output: true
Explanation: "amanaplanacanalpanama" is a palindrome.
Example 2:

Input: s = "race a car"
Output: false
Explanation: "raceacar" is not a palindrome.
Example 3:

Input: s = " "
Output: true
Explanation: s is an empty string "" after removing non-alphanumeric characters.
Since an empty string reads the same forward and backward, it is a palindrome.
 

Constraints:

1 <= s.length <= 2 * 105
s consists only of printable ASCII characters.


Solution:

class Solution
{
public:
    bool isPalindrome(string s)
    {
        string c = "";
        char a;
        for (int i = 0; i < s.size(); i++)
        {
            a = s[i];
            if ((int)a > 47 && (int)a < 58)
                c += a;
            else if ((int)a > 96 && (int)a < 123)
                c += a;
            else if ((int)a > 64 && (int)a < 91)
                c += char((int)a + 32);    // conversion of capital letter into small letter
        }
        return ispalindrome(c);
    }
    bool ispalindrome(string s)
    {
        int l = 0, h = s.size() - 1;
        while (l < h)
        {
            if (s[l++] != s[h--])
                return false;
        }
        return true;
    }
};


















#include<string>
#include<iostream>
#include<vector>
using namespace std;
class Solution {
private:
    bool valid(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 a) {
    int s = 0;
    int e = a.length()-1;

    while(s<=e) {
        if(a[s] != a[e])
        {
            return 0;       
        }
        else{
            s++;
            e--;
        }
    }
    return 1;
}
public:
    bool isPalindrome(string s) {
        
        //faltu character hatado
        string temp = "";
        
        for(int j=0; j<s.length(); j++) {   
            if(valid(s[j])) {
                temp.push_back(s[j]);
            }
        }
        
        //lowercase me kardo
        for(int j=0; j<temp.length(); j++) { 
            temp[j] = toLowerCase(temp[j]);
        }
        
        //check palindrome
        return checkPalindrome(temp);
        
    }
};