Leetcode valid palindrome

palindrom.java

class Solution {

public boolean isPalindrome(String s) {



StringBuilder tmp = new StringBuilder();

//Time Complexity: O(n)
for(char c: s.toCharArray()) {	

	     if(Character.isLetterOrDigit(c)) {

	        tmp.append(Character.toLowerCase(c));
	     }  
}

//Time Complexity O(n)

int n = tmp.length();

for(int i = 0; i < n/2; i++) {
	
	    if(tmp.charAt(i) != tmp.charAt(n-i-1)) return false;
}

//amanaplanacanalpanama //based-0 index
//0


return true;
}


public static void main(String[] args) {
	

	   Solution sol = new Solution();


	   System.out.println(sol.isPalindrome("A man, a plan, a canal: Panama")); //TRUE
	   System.out.println(sol.isPalindrome("Race a Car")); //FALSE
}

}

//A man, a plan, a canal: Panama
//tmp.add(a)
//tmp.add(m)
//tmp.add(a)
//tmp.add(n)
//tmp.add(a)
//tmp.add(p)
//tmp.add(l)
//tmp.add(a)
//tmp.add(n)
//tmp.add(a)
//tmp.add(c)
//tmp.add(a)
//tmp.add(n)
//tmp.add(a)
//tmp.add(l)
//tmp.add(p)
//tmp.add(a)
//tmp.add(n)
//tmp.add(a)
//tmp.add(m)
//tmp.add(a)