DSA · Theory

Breadth First Search Algorithm

Theory

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Breadth First Search Algorithm

Breadth First Search Algorithm is a DSA topic. In plain words you use it for find roll 12 in a sorted list. Don’t start with a slogan — start with that picture.

Smallest example: linear vs binary. Type it, run it, and say what you see. If you can do that from memory, you know Breadth First Search Algorithm.

From the example next to this theory — Breadth First Search Algorithm — bFS explores level by level using a queue.

Trap — binary search on unsorted data. Fix that before you talk about advanced DSA.

Viva — what is Breadth First Search Algorithm? Then show linear vs binary. Then name the trap.

Exam tip

What is Breadth First Search Algorithm? Show this: linear vs binary. Trap: binary search on unsorted data.

Example

from collections import deque

graph = {1: [2, 3], 2: [4], 3: [], 4: []}

def bfs(start):
    seen, q = {start}, deque([start])
    order = []
    while q:
        u = q.popleft()
        order.append(u)
        for v in graph[u]:
            if v not in seen:
                seen.add(v)
                q.append(v)
    return order

print(bfs(1))

Breadth First Search Algorithm — bFS explores level by level using a queue.

Short notes

DefBreadth First Search Algorithm — find roll 12 in a sorted list.
Rulelinear vs binary
Trapbinary search on unsorted data
Usea sorted list

from collections import deque graph = {1: [2, 3], 2: [4], 3: [], 4: []} def bfs(start): seen, q = {start}, deque([start]) order = [] while q: u = q.popleft() order.append(u) for v in graph[u]: if v not in seen: seen.add(v) q.append(v) return order print(bfs(1))

Breadth First Search Algorithm

Example

Short notes

Questions

Breadth First Search Algorithm

Example

Short notes

Questions