1A graph consists of a set of vertices and a set of edges . If the edges have a direction associated with them, the graph is called a:
A.Simple Graph
B.Undirected Graph
C.Directed Graph (Digraph)
D.Connected Graph
Correct Answer: Directed Graph (Digraph)
Explanation:A directed graph or digraph is a graph in which edges have orientations, meaning they are ordered pairs of vertices.
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2According to the Handshaking Lemma, the sum of degrees of all vertices in an undirected graph is equal to:
A.The number of edges
B.Twice the number of edges
C.Half the number of edges
D.The number of vertices
Correct Answer: Twice the number of edges
Explanation:The Handshaking Lemma states that , because every edge contributes exactly 2 to the total degree sum.
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3In a simple undirected graph, the maximum number of edges with vertices is:
A.
B.
C.
D.
Correct Answer:
Explanation:This corresponds to a complete graph , where every vertex is connected to every other distinct vertex.
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4A vertex with a degree of 0 is called a(n):
A.Pendant vertex
B.Isolated vertex
C.Cut vertex
D.Regular vertex
Correct Answer: Isolated vertex
Explanation:An isolated vertex is a vertex that is not connected to any other vertex, hence its degree is 0.
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5A vertex with a degree of 1 is called a:
A.Root vertex
B.Isolated vertex
C.Pendant vertex
D.Null vertex
Correct Answer: Pendant vertex
Explanation:A pendant vertex (or leaf node) is a vertex with exactly one edge connecting it to the rest of the graph.
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6Which of the following statements is true regarding the number of vertices with odd degrees in an undirected graph?
A.There must be an odd number of such vertices.
B.There must be an even number of such vertices.
C.There can be any number of such vertices.
D.There are no vertices with odd degrees.
Correct Answer: There must be an even number of such vertices.
Explanation:This is a corollary of the Handshaking Lemma. Since the total sum of degrees is even (), the number of vertices with odd degrees must be even.
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7A Complete Graph is a simple graph where:
A.There is exactly one path between any pair of vertices.
B.Every pair of distinct vertices is connected by a unique edge.
C.The graph forms a closed loop.
D.The set of vertices can be partitioned into two disjoint sets.
Correct Answer: Every pair of distinct vertices is connected by a unique edge.
Explanation:A complete graph is a simple undirected graph in which every pair of distinct vertices is connected by a unique edge.
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8How many edges does the cycle graph (where ) have?
A.
B.
C.
D.
Correct Answer:
Explanation:A cycle graph consists of vertices and edges forming a single closed loop.
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9A Regular Graph is a graph where:
A.Every vertex has the same degree.
B.Every edge has the same weight.
C.The graph is connected.
D.There are no cycles.
Correct Answer: Every vertex has the same degree.
Explanation:In a -regular graph, every vertex has exactly degree .
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10A Wheel Graph is obtained by taking a cycle graph and adding:
A.One edge connecting two existing vertices.
B.One additional vertex connected to all existing vertices.
C.Another cycle graph.
D.Two additional vertices connected to each other.
Correct Answer: One additional vertex connected to all existing vertices.
Explanation:A wheel graph consists of vertices: the vertices of plus a 'hub' vertex connected to all vertices of the cycle.
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11How many vertices and edges does the Wheel Graph have? (Note: definition assumes is the size of the outer cycle)
A. vertices and edges
B. vertices and edges
C. vertices and edges
D. vertices and edges
Correct Answer: vertices and edges
Explanation: has the vertices of the cycle plus 1 hub vertex ( total). It has edges from the cycle plus spokes ( total).
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12The -dimensional Hypercube (or -cube), denoted , has how many vertices?
A.
B.
C.
D.
Correct Answer:
Explanation:An -cube has vertices, representing all bit strings of length .
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13What is the degree of every vertex in the -cube ?
A.2
B.
C.
D.
Correct Answer:
Explanation:The -cube is an -regular graph. Each bit string of length differs from exactly other strings by exactly one bit.
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14A graph is Bipartite if and only if:
A.It contains no cycles.
B.It is a complete graph.
C.Its vertex set can be partitioned into two disjoint sets such that every edge connects a vertex in one set to one in the other.
D.Every vertex has an even degree.
Correct Answer: Its vertex set can be partitioned into two disjoint sets such that every edge connects a vertex in one set to one in the other.
Explanation:This is the definition of a bipartite graph. Equivalently, it contains no odd cycles.
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15Which of the following Cycle graphs is Bipartite?
A.
B.
C.
D.
Correct Answer:
Explanation:A graph is bipartite if and only if it contains no odd cycles. are odd cycles. is an even cycle.
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16A Complete Bipartite Graph has how many edges?
A.
B.
C.
D.
Correct Answer:
Explanation:In , every vertex in the set of size is connected to every vertex in the set of size , resulting in edges.
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17If a graph has vertices, what is the dimension of its Adjacency Matrix?
A.
B.
C.
D.
Correct Answer:
Explanation:The adjacency matrix is a square matrix of size where rows and columns represent vertices.
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18For a simple undirected graph, the adjacency matrix is always:
A.Asymmetric
B.Symmetric
C.Identity
D.Zero matrix
Correct Answer: Symmetric
Explanation:Since edges are undirected, if vertex is connected to (), then is connected to (), making the matrix symmetric.
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19In the adjacency matrix of a graph, the sum of the entries in row represents:
A.The number of vertices in the graph.
B.The degree of vertex (for undirected graphs).
C.The number of paths of length 2.
D.The weight of the edges.
Correct Answer: The degree of vertex (for undirected graphs).
Explanation:Summing the row counts the number of 1s, which corresponds to the number of edges adjacent to that vertex.
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20Let be the adjacency matrix of a graph . The entry in the matrix (matrix raised to power ) represents:
A.The distance between and .
B.The number of paths of length exactly from to .
C.The number of edges between and .
D.Whether and are connected.
Correct Answer: The number of paths of length exactly from to .
Explanation:This is a fundamental property of the adjacency matrix. counts the number of walks/paths of length between vertices and .
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21An Incidence Matrix for an undirected graph with vertices and edges has dimensions:
A.
B.
C.
D.
Correct Answer:
Explanation:Rows represent vertices and columns represent edges (or vice-versa depending on convention, but is standard for if vertex is incident to edge ).
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22In an incidence matrix for a simple undirected graph, the sum of entries in any column is:
A.1
B.2
C.The degree of the vertex
D.Variable
Correct Answer: 2
Explanation:Each edge (column) connects exactly two vertices, so there are exactly two 1s in each column.
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23Two graphs and are Isomorphic if:
A.They have the same number of vertices and edges.
B.They have the same degree sequence.
C.There exists a bijection between their vertex sets preserving adjacency.
D.Their adjacency matrices are identical.
Correct Answer: There exists a bijection between their vertex sets preserving adjacency.
Explanation:Isomorphism requires a one-to-one correspondence such that .
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24Which of the following is an invariant property preserved under graph isomorphism?
A.The labels of the vertices.
B.The exact visual drawing of the graph.
C.The degree sequence of the graph.
D.The order of vertices in the adjacency matrix.
Correct Answer: The degree sequence of the graph.
Explanation:If two graphs are isomorphic, the number of vertices with a specific degree must be the same in both graphs.
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25A Walk in a graph where no edges are repeated is called a:
A.Path
B.Trail
C.Circuit
D.Cycle
Correct Answer: Trail
Explanation:A walk is a sequence of vertices/edges. A trail is a walk with no repeated edges. A simple path is a walk with no repeated vertices.
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26A path that starts and ends at the same vertex is called a:
A.Simple Path
B.Tree
C.Circuit (or Cycle)
D.Bridge
Correct Answer: Circuit (or Cycle)
Explanation:A circuit is a closed trail (starts and ends at same vertex). A cycle is a closed path (no repeated vertices except start/end).
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27An undirected graph is called Connected if:
A.Every vertex has a degree .
B.There is a path between every pair of distinct vertices.
C.It contains a cycle.
D.It is a complete graph.
Correct Answer: There is a path between every pair of distinct vertices.
Explanation:Connectivity implies the graph is in 'one piece'; you can travel from any node to any other node.
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28A directed graph is Strongly Connected if:
A.There is a path between every pair of vertices in the underlying undirected graph.
B.There is a directed path from to and from to for every pair of vertices .
C.Every vertex has an out-degree of at least 1.
D.It contains no directed cycles.
Correct Answer: There is a directed path from to and from to for every pair of vertices .
Explanation:Strong connectivity requires navigability in both directions between any two nodes following the edge directions.
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29A directed graph is Weakly Connected if:
A.The underlying undirected graph is connected.
B.It is strongly connected.
C.Every node has in-degree 1.
D.It is a set of disjoint components.
Correct Answer: The underlying undirected graph is connected.
Explanation:Weak connectivity means the graph is connected if you ignore the direction of the edges.
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30A vertex whose removal increases the number of connected components in a graph is called a:
A.Pendant vertex
B.Cut vertex (Articulation Point)
C.Isolated vertex
D.Source vertex
Correct Answer: Cut vertex (Articulation Point)
Explanation:Removing a cut vertex disconnects the graph or increases the number of disjoint subgraphs.
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31An edge whose removal increases the number of connected components is called a:
A.Cycle edge
B.Loop
C.Bridge (or Cut Edge)
D.Parallel edge
Correct Answer: Bridge (or Cut Edge)
Explanation:A bridge is an edge that, if deleted, disconnects the graph.
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32Dijkstra’s Algorithm is used to find:
A.The Minimum Spanning Tree.
B.The shortest path from a single source to all other vertices.
C.The shortest path between all pairs of vertices.
D.The topological sort of a graph.
Correct Answer: The shortest path from a single source to all other vertices.
Explanation:Dijkstra's algorithm solves the single-source shortest path problem in graphs.
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33Dijkstra’s algorithm requires that the edge weights are:
A.Integers
B.Positive
C.Non-negative
D.Negative
Correct Answer: Non-negative
Explanation:Dijkstra's algorithm fails if there are negative edge weights (unlike Bellman-Ford), as it assumes adding an edge never decreases total distance.
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34What data structure is most efficiently used to select the next vertex with the minimum distance in Dijkstra’s algorithm?
A.Stack
B.Queue
C.Priority Queue (or Min-Heap)
D.Linked List
Correct Answer: Priority Queue (or Min-Heap)
Explanation:A Min-Priority Queue allows extracting the vertex with the smallest tentative distance efficiently.
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35In Dijkstra's algorithm, the operation of updating the distance of a neighbor of the current vertex is called:
A.Relaxation
B.Contraction
C.Expansion
D.Rotation
Correct Answer: Relaxation
Explanation:Relaxation checks if reaching via is shorter than the currently known path to . If so, update .
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36What is the time complexity of Dijkstra’s algorithm using a binary heap for a graph with vertices and edges?
A.
B.
C.
D.
Correct Answer:
Explanation:With a binary heap, each edge is processed once, and priority queue operations take logarithmic time relative to vertices.
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37Which algorithm strategy does Dijkstra's algorithm follow?
A.Dynamic Programming
B.Divide and Conquer
C.Greedy Approach
D.Backtracking
Correct Answer: Greedy Approach
Explanation:It locally selects the unvisited vertex with the smallest distance at every step, which guarantees the global optimum for non-negative weights.
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38The complement of a simple graph has the same vertex set as , and two vertices are connected in if and only if:
A.They are connected in .
B.They are NOT connected in .
C.One is a neighbor of the other in .
D.They have the same degree in .
Correct Answer: They are NOT connected in .
Explanation:The complement graph contains all the edges required to make a complete graph, excluding the edges already present in .
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39What is the size of the Edge set for ?
A.5
B.10
C.20
D.25
Correct Answer: 10
Explanation:For , edges = . For , .
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40A simple graph is Planar if:
A.It can be drawn in the plane without edges crossing.
B.It is connected.
C.It is bipartite.
D.It has fewer than 5 vertices.
Correct Answer: It can be drawn in the plane without edges crossing.
Explanation:Planarity refers to the geometric representation where edges intersect only at their endpoints.
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41Which graph is known as the Peterson Graph?
A.
B.
C.A specific graph with 10 vertices and 15 edges
D.
Correct Answer: A specific graph with 10 vertices and 15 edges
Explanation:The Peterson graph is a famous counterexample in graph theory, appearing as a pentagram inside a pentagon.
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42The in-degree of a vertex in a directed graph is:
A.The number of edges leaving the vertex.
B.The number of edges entering the vertex.
C.The total number of edges connected to the vertex.
D.Always equal to the out-degree.
Correct Answer: The number of edges entering the vertex.
Explanation:In a directed graph (digraph), in-degree counts edges pointing to the vertex.
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43For any directed graph, the sum of in-degrees is equal to:
A.The sum of out-degrees.
B.Twice the number of edges.
C.The number of vertices.
D.Zero.
Correct Answer: The sum of out-degrees.
Explanation:Every directed edge has exactly one start (contributing to out-degree) and one end (contributing to in-degree). Both sums equal .
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44What is the maximum number of edges in a simple bipartite graph with sets of size and ?
A.
B.
C.
D.
Correct Answer:
Explanation:This corresponds to the complete bipartite graph .
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45A graph with no loops and no parallel edges is called a:
A.Multigraph
B.Pseudograph
C.Simple Graph
D.Weighted Graph
Correct Answer: Simple Graph
Explanation:By definition, a simple graph forbids self-loops and multiple edges between the same pair of vertices.
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46The length of a path in a graph is defined as:
A.The number of vertices in the path.
B.The number of edges in the path.
C.The sum of degrees of vertices in the path.
D.The number of vertices minus one.
Correct Answer: The number of edges in the path.
Explanation:Standard definition: path length corresponds to the number of steps (edges) taken.
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47Two distinct vertices and are adjacent if:
A.There is a path between them.
B.There is an edge connecting them directly.
C.They have the same degree.
D.They belong to the same component.
Correct Answer: There is an edge connecting them directly.
Explanation:Adjacency implies a direct connection via a single edge.
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48If the adjacency matrix of a graph contains 1s on the main diagonal, it indicates the graph has:
A.Cycles
B.Self-loops
C.Parallel edges
D.Disconnected components
Correct Answer: Self-loops
Explanation:Entry means there is an edge from vertex to itself.
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49Which of the following is NOT a necessary condition for two graphs to be isomorphic?
A.Same number of vertices
B.Same number of edges
C.Same number of circuits of a particular length
D.Same adjacency matrix representation without reordering
Correct Answer: Same adjacency matrix representation without reordering
Explanation:Isomorphic graphs generally have different adjacency matrices unless the vertices are labeled in the exact corresponding order. The matrices are permutation-similar, not necessarily identical.
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50In a directed graph, a path is simple if:
A.All edges are distinct.
B.All vertices are distinct.
C.Only the start and end vertices are the same.
D.The direction of edges is ignored.
Correct Answer: All vertices are distinct.
Explanation:A simple path does not repeat vertices.
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