Leetcode: Valid Palindrome (12ms)(string)(two pointers)

PROBLEM:
https://leetcode.com/problems/valid-palindrome/



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See what's Palindrome here. Basically means that you can read forwards or backward and you get the same thing, like: level.

Two pointers.
Transform all into lower case first, then process one by one.

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// codes

class Solution {

public:

       bool isPalindrome(string s) {

              int len = s.size(), l = 0, r = len - 1;

              //check input

              //if (len <= 1) return true;

              //transform to the lower case

              for (int i = 0; i < len; i++){

                     if (s[i] >= 'A' && s[i] <= 'Z')

                           s[i] = s[i] + 32;

              }

              while (l<r){

                     while (l<len){

                           if (s[l] >= 'a' && s[l] <= 'z' || s[l] >= '0' && s[l] <= '9')break;

                           else l++;

                           if (l == len)return true;

                     }

                     while (r>-1){

                           if (s[r] >= 'a' && s[r] <= 'z' || s[r] >= '0' && s[r] <= '9')break;

                           else r--;

                           //if(r==-1)return true;

                     }

                     if (s[l] != s[r])return false;

                     l++;

                     r--;

              }

              return true;

       }

};