[LeetCode] Valid Palindrome [10]
2014-06-06 14:46
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题目
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.
原题地址
解题思路
验证一个字符串是否是回文字符串。首先看看wiki上对于回文的解释:回文,亦称回环,是正读反读都能读通的句子,亦有将文字排列成圆圈者,Famous examples include "Amore, Roma", "A man, a plan, a canal: Panama" and "No 'x' in 'Nixon'"。判读一个字符串是否是回文,一种方法可以将字符串倒置然后和原字符串进行比较。这里采用一种类似字符串翻转的方法,通过从前后两个方向来比较判断是否是回文。本题中的有效字符是字母和数字,并且忽略字母大小写。
代码如下
class Solution { public: bool isPalindrome(string s) { int n = s.size(); int i=0, j=n-1; while(i<j){ if( !isalpha(s[i]) ) { ++i; continue; } if( !isalpha(s[j]) ) { --j; continue; } if(s[i] != s[j]) return false; ++i,--j; } return true; } //判断是否是字母数字,如果是大写字母则将其转化为小写字母 bool isalpha(char &c){ if((c>='A'&&c<='Z')){ c = c-'A'+'a'; return true; } return (c>='a'&&c<='z') || (c>='0'&&c<='9'); } };
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(转载文章请注明出处: http://blog.csdn.net/swagle/article/details/28883129 )
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