DSA · Theory

Depth First Search Algorithm

Theory

39/810

Depth First Search Algorithm

Depth 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 Depth First Search Algorithm.

From the example next to this theory: Depth First Search Algorithm — dFS goes deep along a path before backtracking — natural with recursion/stack.

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

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

Exam tip

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

Example

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

def dfs(u, seen=None):
    if seen is None:
        seen = set()
    seen.add(u)
    order = [u]
    for v in graph[u]:
        if v not in seen:
            order += dfs(v, seen)
    return order

print(dfs(1))

Depth First Search Algorithm — dFS goes deep along a path before backtracking — natural with recursion/stack.

Short notes

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

DSA · Theory

Depth First Search Algorithm

← All stacks

Theory

39/810

Depth First Search Algorithm

Depth 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 Depth First Search Algorithm.

From the example next to this theory: Depth First Search Algorithm — dFS goes deep along a path before backtracking — natural with recursion/stack.

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

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

Exam tip

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

Example

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

def dfs(u, seen=None):
    if seen is None:
        seen = set()
    seen.add(u)
    order = [u]
    for v in graph[u]:
        if v not in seen:
            order += dfs(v, seen)
    return order

print(dfs(1))

Depth First Search Algorithm — dFS goes deep along a path before backtracking — natural with recursion/stack.

Short notes

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

Depth First Search Algorithm

Example

Short notes

Questions

Depth First Search Algorithm

Example

Short notes

Questions