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'.

最多删掉一个字符，判断这个字符串是不是回文串。

C++（145ms）：

class Solution {
public:
    bool valid(string& s, int i, int j, int d) { 
        if (i >= j)
            return true ;
        if (s[i] == s[j])
            return valid(s,i+1,j-1,d) ;
        else
            return d > 0 &&(valid(s,i+1,j,d-1) || valid(s,i,j-1,d-1));
    }
    
    bool validPalindrome(string s) {
        return valid(s,0,s.length()-1,1) ;
    }

};

Java(57ms):

class Solution {
    public boolean validPalindrome(String s) {
        int left = 0 ;
        int right = s.length()-1 ;
        while(left <= right){
            if (s.charAt(left) != s.charAt(right)){
                return valid(s,left+1,right) || valid(s,left,right-1);
            }
            left++ ;
            right-- ;
        }
        return true ;
    }
    
    public boolean valid(String s,int left , int right) {
        while(left <= right){
            if (s.charAt(left) == s.charAt(right)){
                left++ ;
                right-- ;
            }else{
                return false ;
            }
            
        }
        return true ;
    }
}