ملاحظة قراءة الخوارزمية

Best Time to Buy/Sell Stocks

For the one-transaction stock problem, scan once while tracking the minimum price seen so far and the best profit achievable by selling today.

النوعخوارزميةالفئةClassic Problemsالعمقمبتدئالتعقيد المعتادVaries by implementation / input constraints

إجابة مقابلة قصيرة

ابدأ بهذا النموذج الذهني

For the one-transaction stock problem, scan once while tracking the minimum price seen so far and the best profit achievable by selling today.

شرح مبسط

كيف يعمل، بلا مصطلحات زائدة

The buy must occur before the sell, so only past minimums are valid buy candidates.

One pass gives O(n) time and O(1) extra space.

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 Best Time to Buy/Sell Stocks, the goal is to make the invariant visible rather than to memorize code.

تطبيق JavaScript قابل للقراءةJavaScript

function maxProfit(prices) {
  let minPrice = Infinity;
  let best = 0;
  for (const price of prices) {
    minPrice = Math.min(minPrice, price);
    best = Math.max(best, price - minPrice);
  }
  return best;
}

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Do not quote this complexity mechanically.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

Do not sort prices; sorting destroys time order. Track the best historical buy price instead.

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

فحص سريع للمقابلة

What problem does Best Time to Buy/Sell Stocks solve?

For the one-transaction stock problem, scan once while tracking the minimum price seen so far and the best profit achievable by selling today.

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 maxProfit(prices) { let minPrice = Infinity; let best = 0; for (const price of prices) { minPrice = Math.min(minPrice, price); best = Math.max(best, price - minPrice); } return best; }