很简单，加入HashSet来进行判断
'''
class Solution {
public boolean validPalindrome(String s) {
int start=0;
int end=s.length()-1;
while(start<end){
if(s.charAt(start)==s.charAt(end)){
start++;
end--;
}else{
return panduan(start,end-1,s)||panduan(start+1,end,s);
}
}
return true;
}
public boolean panduan(int left,int right,String s){
while(left<right){
if(s.charAt(left)==s.charAt(right)){
left++;
right--;
}else{
return false;
}
}
return true;
}
}
'''
