DSA · Theory

Graph Algorithms

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Theory

162/810

Graph Algorithms

If you can teach Graph Algorithms using bus routes, you know it. If you only know the heading, you don’t.

For Graph Algorithms, time vs memory is in play. Don’t blame it until you have traced bus routes.

Without Graph Algorithms, a city map gets messy and bus routes is hard to trust.

Priya ships Graph Algorithms in a city map. That is the use case worth saying.

If bus routes breaks under Graph Algorithms, check no visited set → infinite loop first.

After Graph Algorithms, Priya should still remember no visited set → infinite loop.

Viva for Graph Algorithms — what it is → BFS queue / DFS stack → the mistake (no visited set → infinite loop).

Exam tip

Board: bus routes. Dry-run Graph Algorithms. Name the trap: no visited set → infinite loop.

Example

# adjacency list
graph = {
    "A": [("B", 2), ("C", 5)],
    "B": [("A", 2), ("C", 1)],
    "C": [("A", 5), ("B", 1)],
}
for u, edges in graph.items():
    print(u, "->", edges)

Graph Algorithms — graphs are often stored as adjacency lists: vertex → list of (neighbor, weight).

Short notes

DefGraph Algorithms — Priya uses it for bus routes in a city map.
RuleGraph Algorithms → BFS queue / DFS stack.
RememberGraph Algorithms + time vs memory (a city map).
UseGraph Algorithms in a city map (bus routes).
TrapGraph Algorithms — no visited set → infinite loop.
ExGraph Algorithms → bus routes.

DSA · Theory

Graph Algorithms

← All stacks

Theory

162/810

Graph Algorithms

If you can teach Graph Algorithms using bus routes, you know it. If you only know the heading, you don’t.

For Graph Algorithms, time vs memory is in play. Don’t blame it until you have traced bus routes.

Without Graph Algorithms, a city map gets messy and bus routes is hard to trust.

Priya ships Graph Algorithms in a city map. That is the use case worth saying.

If bus routes breaks under Graph Algorithms, check no visited set → infinite loop first.

After Graph Algorithms, Priya should still remember no visited set → infinite loop.

Viva for Graph Algorithms — what it is → BFS queue / DFS stack → the mistake (no visited set → infinite loop).

Exam tip

Board: bus routes. Dry-run Graph Algorithms. Name the trap: no visited set → infinite loop.

Example

# adjacency list
graph = {
    "A": [("B", 2), ("C", 5)],
    "B": [("A", 2), ("C", 1)],
    "C": [("A", 5), ("B", 1)],
}
for u, edges in graph.items():
    print(u, "->", edges)

Graph Algorithms — graphs are often stored as adjacency lists: vertex → list of (neighbor, weight).

Short notes

DefGraph Algorithms — Priya uses it for bus routes in a city map.
RuleGraph Algorithms → BFS queue / DFS stack.
RememberGraph Algorithms + time vs memory (a city map).
UseGraph Algorithms in a city map (bus routes).
TrapGraph Algorithms — no visited set → infinite loop.
ExGraph Algorithms → bus routes.

Graph Algorithms

Example

Short notes

Questions

Graph Algorithms

Example

Short notes

Questions