c:

#include "stdbool.h"
#include <string.h>

int num = 0;

bool palind(char *s, int left, int right)
{
    if (left == right || left == right + 1)
        return true;
    if (s[left] == s[right])
        return palind(s, left + 1, right - 1);
    if (num == 1)
        return false;
    num++;
    
 
return palind(s, left + 1, right) || palind(s, left, right - 1);
}

bool validPalindrome(char *s)
{
    if (s[0] == '\0')
        return true;
    return palind(s, 0, strlen(s) - 1);
}

　　JAVA:

    int num = 0;

    public boolean validPalindrome(String s) {
        int len = s.length(), left = 0, right = len - 1;
        
 
return palind(s, left, right);
    }

    private boolean palind(String s, int left, int right) {
        if (left == right || left == right + 1) return true;
        if (s.charAt(left) == s.charAt(right)) return palind(s, left + 1, right - 1);
        if (num == 1) return false;
        num++;
        
 
return palind(s, left, right - 1) || palind(s, left + 1, right);
    }

　　JS:

/**
 * @param {string} s
 * @return {boolean}
 */
var validPalindrome = function (s) {
    if (!s || s.length == 0) return true;
    return palind(s, 0, s.length - 1);
};

var num = 0;

var palind = function (s, left, right) {
    if (left == right || left == right + 1) return true;
    if (s.charAt(left) == s.charAt(right)) return palind(s, left + 1, right - 1);
    if (num == 1) return false;
    num ++;
    return palind(s, left + 1, right) || palind(s, left, right - 1);
}