680. Valid Palindrome II

Given a non-empty string s, you may delete at most one character. Judge whether you can make it a palindrome.

Example 1:

Input: "aba"
Output: True

Example 2:

Input: "abca"
Output: True
Explanation: You could delete the character 'c'.

Note:

1. The string will only contain lowercase characters a-z. The maximum length of the string is 50000. 

time: O(n), space: O(1)

class Solution {
    public boolean validPalindrome(String s) {
        int l = 0, r = s.length() - 1;
        while(l <= r) {
            if(s.charAt(l) != s.charAt(r))
                return valid(s, l + 1, r) || valid(s, l, r - 1);
            l++;
            r--;
        }
        return true;
    }
    private boolean valid(String s, int start, int end) {
        int l = start, r = end;
        while(l <= r) {
            if(s.charAt(l) != s.charAt(r))
                return false;
            l++;
            r--;
        }
        return true;
    }
}