LeetCode-Solutions-in-Cpp17

Solutions to high-frequency interview questions of LeetCode in C++17, taking into account both efficiency and comprehensibility.

---

Project maintained by downdemo Hosted on GitHub Pages — Theme by mattgraham

• 用双指针从两侧往中间移动，如果其中出现两侧不等的情况，则不是回文串

abcddba
|     |
l     r

abcddba
 |   |
 l   r

abcddba
  | |
  l r
不等，因此不是回文串

• 题目只考虑字母和数字字符，忽略大小写，对这些情况进行处理即可

class Solution {
 public:
  bool isPalindrome(string s) {
    int l = 0;
    int r = size(s) - 1;
    while (l < r) {
      while (l < r && !isalnum(s[l])) {
        ++l;
      }
      while (l < r && !isalnum(s[r])) {
        --r;
      }
      if (toupper(s[l]) == toupper(s[r])) {
        ++l;
        --r;
      } else {
        return false;
      }
    }
    return true;
  }
};