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　　去年就在某牛人的博客上见到了，现在准备去玩玩。做题的方式跟Topcoder类似，刚刚去水了一题"Valid Palindrome"

 1 class Solution {
 2 public:
 3     bool isPalindrome(string s) {
 4         // Start typing your C/C++ solution below
 5         // DO NOT write int main() function
 6         string alnumstr;
 7         transform(s.begin(), s.end(), s.begin(), [](char& ch){ return ::toupper(ch);});
 8         copy_if(s.begin(), s.end(), back_inserter(alnumstr), [](char& ch){ return ::isalnum(ch);});
 9         
10         string another;
11         reverse_copy(alnumstr.begin(), alnumstr.end(), back_inserter(another));
12         
13         return another == alnumstr;
14         
15     }
16 };

 1 class Solution {
 2 public:
 3     bool isPalindrome(string s) {
 4         // Start typing your C/C++ solution below
 5         // DO NOT write int main() function
 6 
 7         const char* str = s.c_str();
 8         for (int i = 0, j = strlen(str); i < j; )
 9         {
10             if (isalnum(str[i]) && isalnum(str[j]))
11             {
12                 if (toupper(str[i]) != toupper(str[j]))
13                 {
14                     return false;
15                 }
16                 else
17                 {
18                     ++i;
19                     --j;
20                 }
21             }
22             if (!isalnum(str[i])) ++i;
23             if (!isalnum(str[j])) --j;
24         }
25         return true;
26         
27     }
28 };