Palindrome
A palindrome reads the same forward and backward after applying the problem's normalization rules.
先从这个心智模型开始
A palindrome reads the same forward and backward after applying the problem's normalization rules.
它如何工作，不堆砌不必要的术语
Two pointers can compare characters from both ends in O(n) time and O(1) extra space if normalization is done in-place/logically.
Always clarify whether spaces, punctuation and letter case should be ignored.
把算法读成一连串决策
Clarify Unicode/case/normalization assumptions.
Define indexes or prefix state.
Reuse previously learned match information when the algorithm allows it.
Read a tiny input by hand and write down the state after every important operation. For Palindrome, the goal is to make the invariant visible rather than to memorize code.
function isPalindrome(text) {
const s = text.toLowerCase().replace(/[^a-z0-9]/g, "");
let l = 0, r = s.length - 1;
while (l < r) {
if (s[l++] !== s[r--]) return false;
}
return true;
}不要死记语法。跟踪每一行中发生变化的状态，并把它与上面描述的不变量联系起来。
Varies by implementation / input constraints
Do not quote this complexity mechanically. Ask which operation or input dimension it describes, then derive the cost from the loops, recursion depth, data-structure operations and any preprocessing assumptions.
适用场景
- Use specialized matching algorithms when repeated or large-string searching makes naive scanning too expensive.
通常哪里会出错
- Ignoring Unicode semantics.
- Confusing substring with subsequence.
- Off-by-one prefix/index bugs.
专业回答结构
Clarify input rules first; many wrong solutions solve a different normalization problem than the interviewer asked.
What problem does Palindrome solve?
A palindrome reads the same forward and backward after applying the problem's normalization rules.
关于复杂度应该提到什么？
Its typical cost here is Varies by implementation / input constraints, but a complete answer should connect that cost to the representation, input constraints and the dominant operations.
最常见的错误是什么？
Ignoring Unicode semantics.