Practice Question
Duration: 2 min
This video lesson is available to enrolled students.
AI Summary
An AI-generated summary of this video lecture.
The lecture addresses a graph theory problem asking for the count of simple non-isomorphic graphs with 5 vertices and 3 edges. The instructor systematically enumerates possible configurations by drawing labeled vertex sets (a, b, c, d, e) and constructing distinct edge arrangements. Four unique structures are identified: a path graph of length 3, a triangle (cycle C3) with isolated vertices, a star graph K1,3, and a disjoint union of an edge and a path. The visual progression demonstrates how to distinguish non-isomorphic cases based on connectivity and component structure.
Chapters
0:00 – 2:00 00:00-02:00
The instructor introduces the problem statement displayed on screen: 'Q How many simple non isomorphic graphs are possible with 5 vertices and 3 edges?'. He begins by labeling five points (a, b, c, d, e) on the screen to represent vertices. The visual progression shows him setting up multiple sets of these labeled points, indicating he is preparing to draw different graph configurations systematically. He then draws four distinct diagrams: Graph 1 shows a path of length 3 with an isolated vertex; Graph 2 shows a triangle (cycle C3) with two isolated vertices; Graph 3 shows a central vertex connected to three others (star graph K1,3) with one isolated vertex; Graph 4 shows a path of length 2 and a separate edge. These drawings illustrate the variety of possible structures satisfying the vertex and edge constraints.
2:00 – 2:06 02:00-02:06
The final frames display the completed set of four labeled graphs (1, 2, 3, 4) alongside the problem statement. The whiteboard shows 'SANCHIT JAIN SIR' as a watermark, confirming the instructor's identity. The visual evidence concludes the enumeration phase of the problem, presenting the four distinct non-isomorphic configurations derived from systematic construction using labeled vertices a through e.
This session focuses on combinatorial enumeration in graph theory, specifically identifying non-isomorphic simple graphs under fixed vertex and edge counts. The instructor employs a constructive method, starting with labeled vertices to ensure clarity in distinguishing structural differences. Key concepts include isomorphism (structural equivalence), simple graphs (no loops or multiple edges), and connectivity components. The four solutions represent all possible partitions of 3 edges among 5 vertices without creating isomorphic duplicates. The path graph (P4) and disjoint union (P3 + K2) highlight how edge distribution affects component count. The triangle (C3) and star graph (K1,3) demonstrate how cycles and centralization create unique topologies. This systematic approach ensures no valid configuration is missed while avoiding overcounting due to symmetry.