ملاحظة قراءة الخوارزمية

Valid Parentheses

Valid Parentheses checks whether every opening bracket is closed by the matching bracket in the correct nesting order. A stack models that nesting naturally.

النوعخوارزميةالفئةClassic Problemsالعمقمبتدئالتعقيد المعتادVaries by implementation / input constraints

إجابة مقابلة قصيرة

ابدأ بهذا النموذج الذهني

Valid Parentheses checks whether every opening bracket is closed by the matching bracket in the correct nesting order. A stack models that nesting naturally.

شرح مبسط

كيف يعمل، بلا مصطلحات زائدة

Push opening brackets.

For each closing bracket, pop and verify that it matches. At the end the stack must be empty.

التنفيذ

اقرأ الخوارزمية كسلسلة من القرارات

Restate constraints and edge cases.

Identify the pattern and invariant.

Walk through a small example before coding.

مثال صغير لتحتفظ به في ذهنك

Read a tiny input by hand and write down the state after every important operation. For Valid Parentheses, the goal is to make the invariant visible rather than to memorize code.

تطبيق JavaScript قابل للقراءةJavaScript

function isValid(input) {
  const match = { ")": "(", "]": "[", "}": "{" };
  const stack = [];
  for (const ch of input) {
    if ("([{ ".includes(ch) && ch !== " ") stack.push(ch);
    else if (match[ch] && stack.pop() !== match[ch]) return false;
  }
  return stack.length === 0;
}

كيف تقرأ هذا الكود

لا تحفظ الصياغة. تتبع الحالة التي تتغير في كل سطر واربطها بالثابت الموضح أعلاه.

التعقيد

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Do not quote this complexity mechanically.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.

متى تستخدمه

مناسب لـ

Use the recognized pattern when its invariant matches the problem constraints.

أخطاء شائعة

ما الذي يسوء عادةً

Jumping to code before defining the invariant.
Optimizing before producing a correct baseline.

كيف تشرحه في المقابلة

صيغة إجابة احترافية

This is a classic example of choosing a data structure from the problem's structure: nested last-opened-first-closed behavior directly implies a stack.

المشكلة→الفكرة الأساسية→الثابت / الحالة→Big-O→المفاضلة

فحص سريع للمقابلة

What problem does Valid Parentheses solve?

Valid Parentheses checks whether every opening bracket is closed by the matching bracket in the correct nesting order. A stack models that nesting naturally.

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؟

Jumping to code before defining the invariant.

متابعة القراءةProblem patternsEdge casesComplexity trade-offs

function isValid(input) { const match = { ")": "(", "]": "[", "}": "{" }; const stack = []; for (const ch of input) { if ("([{ ".includes(ch) && ch !== " ") stack.push(ch); else if (match[ch] && stack.pop() !== match[ch]) return false; } return stack.length === 0; }