【LeetCode】125. Valid Palindrome

题解：用两指针即可

bool isPalindrome(string s) { int len=s.size(); int lt=0,rt=len-1; while(lt<rt) { while(isalnum(s[lt])==false&<<rt)lt++; while(isalnum(s[rt])==false&<<rt)rt--; if(toupper(s[lt])!=toupper(s[rt]))return false; lt++;rt--; } return true; }