-
Notifications
You must be signed in to change notification settings - Fork 22
Expand file tree
/
Copy path125.valid-palindrome.cpp
More file actions
62 lines (55 loc) · 1.45 KB
/
125.valid-palindrome.cpp
File metadata and controls
62 lines (55 loc) · 1.45 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
// Tag: Two Pointers, String
// Time: O(N)
// Space: O(1)
// Ref: -
// Note: -
// 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.
//
//
class Solution {
public:
bool isPalindrome(string s) {
int l = 0;
int r = s.size() - 1;
while (l < r) {
while (l < r && !isalnum(s[l])) {
l++;
}
while (l < r && !isalnum(s[r])) {
r--;
}
if (tolower(s[l]) != tolower(s[r])) {
return false;
}
l++;
r--;
}
return true;
}
};