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;

}