文章目录
一、题目
125. Valid Palindrome
A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.
Given a string s, return true if it is a palindrome, or false otherwise.
Example 1:
Input: s = "A man, a plan, a canal: Panama"
Output: true
Explanation: "amanaplanacanalpanama" is a palindrome.
Example 2:
Input: s = "race a car"
Output: false
Explanation: "raceacar" is not a palindrome.
Example 3:
Input: s = " "
Output: true
Explanation: s is an empty string "" after removing non-alphanumeric characters.
Since an empty string reads the same forward and backward, it is a palindrome.
Constraints:
1 <= s.length <= 2 * 105
s consists only of printable ASCII characters.
题目来源： leetcode
二、题解
cpp
class Solution {
public:
bool isPalindrome(string s) {
int n = s.length();
string tmp = "";
for(int i = 0;i < n;i++){
if(isdigit(s[i]) || isalpha(s[i])) tmp += s[i];
}
int i = 0,j = tmp.length() - 1;
while(i < j){
if(tolower(tmp[i]) != tolower(tmp[j])) return false;
i++;
j--;
}
return true;
}
};