Palindrome
A palindrome reads the same forward and backward after applying the problem's normalization rules.
ابدأ بهذا النموذج الذهني
A palindrome reads the same forward and backward after applying the problem's normalization rules.
كيف يعمل، بلا مصطلحات زائدة
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.
اقرأ الخوارزمية كسلسلة من القرارات
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;
}لا تحفظ الصياغة. تتبع الحالة التي تتغير في كل سطر واربطها بالثابت الموضح أعلاه.
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Do not quote this complexity mechanically.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.
مناسب لـ
- Use specialized matching algorithms when repeated or large-string searching makes naive scanning too expensive.
ما الذي يسوء عادةً
- Ignoring Unicode semantics.
- Confusing substring with subsequence.
- Off-by-one prefix/index bugs.
صيغة إجابة احترافية
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.
ماذا يجب أن أذكر عن التعقيد؟
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.
ما الخطأ الأكثر شيوعاً؟
Ignoring Unicode semantics.