Stage 1 · Code
Graph Algorithms
Graph Representation
Adjacency matrix, adjacency list, and edge list in Go.
5 min readMastering Data Structures & Algorithms for Software Engineering InterviewsCode
Adjacency Matrix
V×V matrix where matrix[u][v] = 1 (or weight) if edge u→v exists. O(V²) space, O(1) edge check.
Goadjacency-matrix.go
25 linesLn 1, Col 1Go
Matrix[i][j] = weight (0 = no edge). Good for dense graphs, fast edge lookup.
Adjacency List
Array of lists where list[u] contains all neighbors of u. O(V+E) space, O(deg(u)) to iterate neighbors.
Goadjacency-list.go
26 linesLn 1, Col 1Go
Slice of slices. Each Edge has To vertex and Weight. Iterate neighbors with range.
Edge List
Simple list of all edges (u, v, w). O(E) space. Good for algorithms that process all edges (Kruskal, Bellman-Ford).
Goedge-list.go
13 linesLn 1, Col 1Go
Flat edge array. Simple but need to scan all edges for neighbor queries.
Comparison
| Operation | Matrix | List | Edge List |
|---|---|---|---|
| Space | O(V²) | O(V+E) | O(E) |
| Add edge | O(1) | O(1) | O(1) |
| Check edge | O(1) | O(deg(u)) | O(E) |
| Iterate neighbors | O(V) | O(deg(u)) | O(E) |
| Best for | Dense, small V | Sparse, general | Edge-centric algos |
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