ملاحظة قراءة الخوارزمية

Graph Depth-First Search

DFS explores one path as deeply as possible before backtracking. It can be implemented recursively or with an explicit stack.

النوعخوارزميةالفئةGraphsالعمقمبتدئالتعقيد المعتادO(V+E)

إجابة مقابلة قصيرة

ابدأ بهذا النموذج الذهني

DFS explores one path as deeply as possible before backtracking. It can be implemented recursively or with an explicit stack.

شرح مبسط

كيف يعمل، بلا مصطلحات زائدة

Mark a node visited before exploring neighbors to avoid cycles.

Across a graph represented by adjacency lists, traversal is O(V + E).

التنفيذ

اقرأ الخوارزمية كسلسلة من القرارات

Define directed/undirected and weighted/unweighted assumptions.

Choose the graph representation.

Track algorithm state and handle disconnected/cyclic cases explicitly.

مثال صغير لتحتفظ به في ذهنك

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

تطبيق JavaScript قابل للقراءةJavaScript

function dfs(graph, start) {
  const seen = new Set();
  function visit(node) {
    if (seen.has(node)) return;
    seen.add(node);
    for (const next of graph[node] ?? []) visit(next);
  }
  visit(start);
  return seen;
}

كيف تقرأ هذا الكود

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

التعقيد

O(V+E)

Do not quote this complexity mechanically.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

Connectivity
Cycle/SCC building blocks
Backtracking-style graph exploration

أخطاء شائعة

ما الذي يسوء عادةً

Forgetting disconnected components.
Mixing weighted and unweighted shortest-path algorithms.
Not protecting against revisits/cycles.

كيف تشرحه في المقابلة

صيغة إجابة احترافية

State the visited-set requirement and O(V + E). Compare with BFS when shortest unweighted paths are needed.

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

فحص سريع للمقابلة

What problem does Graph Depth-First Search solve?

DFS explores one path as deeply as possible before backtracking. It can be implemented recursively or with an explicit stack.

ماذا يجب أن أذكر عن التعقيد؟

Its typical cost here is O(V+E), but a complete answer should connect that cost to the representation, input constraints and the dominant operations.

ما الخطأ الأكثر شيوعاً؟

Forgetting disconnected components.

متابعة القراءةGraph representationDFS/BFSPriority queues

function dfs(graph, start) { const seen = new Set(); function visit(node) { if (seen.has(node)) return; seen.add(node); for (const next of graph[node] ?? []) visit(next); } visit(start); return seen; }