【125-Valid Palindrome(回文字验证)】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题
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.
题目大意
给定一个字符串，判断它是否是回文字符串，仅考虑字母，并且忽略大小写。
解题思路
使用首尾指针，分别找到第一个符合条件的位置，进行比较，如果相等就进行下一组比较，不相等就返回false，直到所有的字母都处理完。
代码实现
算法实现类
{(String s) {if (s == null) {return false;}int left = 0;int right = s.length() – 1;int delta = ‘A’ – ‘a’;char l;char r;while (left < right) {while (left < s.length() && !isAlphanumericCharacters(s.charAt(left))) { // 从左向右找数字与字母left++;}while (right >= 0 && !isAlphanumericCharacters(s.charAt(right))) { // 从右向左找数字与字母right–;}if (left < right) {l = s.charAt(left);r = s.charAt(right);if (l == r || l – r == delta || r – l == delta) {left++;right–;} else {return false;}}}return true;}/*** 判断是否是字母或者数字** @param c 待判断的数字* @return 判断结果*/(char c) {return c >= ‘0’ && c <= ‘9’ || c >= ‘a’ && c <= ‘z’ || c >= ‘A’ && c <= ‘Z’;}}评测结果
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怀着淡定从容的心态去面对，也就没有了真正意义上的寂寞了。
