ALGORITHMUS-LESENOTIZ

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.

TYPAlgorithmusKATEGORIEClassic ProblemsTIEFEEinsteigerTYPISCHE KOMPLEXITÄTVaries by implementation / input constraints

KURZE INTERVIEWANTWORT

Beginne mit diesem mentalen Modell

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

EINFACHE ERKLÄRUNG

So funktioniert es – ohne unnötigen Jargon

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.

AUSFÜHRUNG

Lies den Algorithmus als Folge von Entscheidungen

Restate constraints and edge cases.

Identify the pattern and invariant.

Walk through a small example before coding.

Ein kleines Beispiel als Orientierung

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.

LESBARE JAVASCRIPT-IMPLEMENTIERUNGJavaScript

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;
}

So liest du diesen Code

Lerne die Syntax nicht auswendig. Folge dem Zustand, der sich in jeder Zeile ändert, und verbinde ihn mit der oben beschriebenen Invariante.

KOMPLEXITÄT

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Do not quote this complexity mechanically.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.

WANN EINSETZEN

Gut geeignet

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

HÄUFIGE FEHLER

Was typischerweise schiefgeht

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

SO ERKLÄRST DU ES IM INTERVIEW

Struktur einer professionellen Antwort

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

Problem→Kernidee→Invariante / Zustand→Big-O→Trade-off

SCHNELLER INTERVIEW-CHECK

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.

Was sollte ich zur Komplexität erwähnen?

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.

Was ist der häufigste Fehler?

Jumping to code before defining the invariant.

WeiterlesenProblem 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; }