leetcode_125题——Valid Palindrome（string，比较常规思路）

Valid Palindrome

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Question Solution

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.

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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;
}