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 * 105s consists only of printable ASCII characters.
class Solution {
public boolean isPalindrome(String s) {
if(s.length()==1){
return true ;
}
StringBuilder sb = new StringBuilder("");
for(int i=0;i<s.length();i++){
char ch = s.charAt(i);
if (ch>='a' && ch<='z'){sb.append(ch);}
else if ( ch>='A' && ch<='Z')
{
ch = (char)(ch-'A'+'a');
sb.append(ch);
}
else if ( ch>='0' && ch<='9')
{
sb.append(ch);
}
}
int start = 0 ;
int end = sb.length()-1;
while(start<end){
int sChar = sb.charAt(start);
int eChar = sb.charAt(end);
if(sChar!=eChar){
return false;
}
start++;
end--;
}
return true ;
}
}
Office:- 660, Sector 14A, Vasundhara, Ghaziabad, Uttar Pradesh - 201012, India
