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Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a palindrome.
Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.
For the purpose of this problem, we define empty string as valid palindrome.
Two Pointers String
这道题，采用先将数字和字母都提取出来，然后再将这些字母一个从前往后，一个从后往前进行比较
#include<iostream>
#include<string>
using namespace std;
bool isPalindrome(string s) {
if(s.empty())
return 1;
int len=s.size();
int i=0;
int flag=0;//作为标志是否全部为空
string temp;
while(i<len)
{
if(s[i]!=‘ ‘)
flag=1;
if((s[i]>=48&&s[i]<=57)||(s[i]>=65&&s[i]<=90)||(s[i]>=97&&s[i]<=122))
temp.push_back(s[i]);
i++;
}
if(flag==0)//若全为空，直接退出
return 1;
int len_temp=temp.size();
i=0;
while(i<len_temp/2)
{
if( (temp[i]==temp[len_temp-i-1])||//比如a=a
((temp[i]>=65&&temp[i]<=97)&&(temp[i]==temp[len_temp-i-1]-32))||//比如a=A
(((temp[i]==temp[len_temp-i-1]+32))&&(temp[i]>=97&&temp[i]<=122))//比如A=a
)
{i++;}
else
return 0;
}
return 1;
}
int main()
{
string str="ab";
cout<<isPalindrome(str)<<endl;
system("pause");
return 1;
}
leetcode_125题——Valid Palindrome（string，比较常规思路）
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原文地址：http://www.cnblogs.com/yanliang12138/p/4442845.html
