SubgraphsProblem DescriptionGiven a graph of N nodes and E bidirectional edges, determine how many disjoint subgraphs there are in the graph. For this case, a portion of a graph is considered a subgraph if any 2 node in the portion are connected directly or indirectly. A node without any edges are also considered as a subgraph. Two disjoint subgraph will not have any edges in between any node of the first subgraph and any node of the second subgraph.The nodes are labelled from 0 to N - 1 and there will not be 2 edges between any 2 pairs of nodes.Input2 integers, N then EE lines consisting of 2 integers each, A and B. 0 ≤ A < B < N.OutputA single integer, which is the number of disjoint subgraphs.LimitsSubtask 1 (45%): N = 1000, 0 ≤ E ≤ 10000.Subtask 2 (55%): N = 1000000, 0 ≤ E ≤ 1000000.Subtask 3 (0%): As per sample testcasesSample Testcase 1Input:5 31 23 44 0Output:2Explanation:The graph above contains 2 disjoint subgraphs: {1, 2} and {0, 3, 4}Sample Testcase 2Input:5 40 11 22 33 4Output:1
Question
SubgraphsProblem DescriptionGiven a graph of N nodes and E bidirectional edges, determine how many disjoint subgraphs there are in the graph. For this case, a portion of a graph is considered a subgraph if any 2 node in the portion are connected directly or indirectly. A node without any edges are also considered as a subgraph. Two disjoint subgraph will not have any edges in between any node of the first subgraph and any node of the second subgraph.The nodes are labelled from 0 to N - 1 and there will not be 2 edges between any 2 pairs of nodes.Input2 integers, N then EE lines consisting of 2 integers each, A and B. 0 ≤ A < B < N.OutputA single integer, which is the number of disjoint subgraphs.LimitsSubtask 1 (45%): N = 1000, 0 ≤ E ≤ 10000.Subtask 2 (55%): N = 1000000, 0 ≤ E ≤ 1000000.Subtask 3 (0%): As per sample testcasesSample Testcase 1Input:5 31 23 44 0Output:2Explanation:The graph above contains 2 disjoint subgraphs: {1, 2} and {0, 3, 4}Sample Testcase 2Input:5 40 11 22 33 4Output:1
Solution
This problem can be solved using the concept of Disjoint Set Union (DSU) or Union-Find data structure. Here are the steps to solve this problem:
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Initialize a DSU with N nodes. In the beginning, each node is a separate component (or subgraph), so the initial number of disjoint subgraphs is N.
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For each edge (A, B), perform the union operation on nodes A and B. This operation merges the two components containing A and B into a single component. If A and B are already in the same component, the operation has no effect.
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After processing all edges, the number of disjoint subgraphs is equal to the number of separate components in the DSU. This can be found by iterating over all nodes and counting the number of unique parent nodes.
Here is a Python code snippet that implements the above steps:
def find(parent, i):
if parent[i] == i:
return i
return find(parent, parent[i])
def union(parent, rank, x, y):
xroot = find(parent, x)
yroot = find(parent, y)
if rank[xroot] < rank[yroot]:
parent[xroot] = yroot
elif rank[xroot] > rank[yroot]:
parent[yroot] = xroot
else :
parent[yroot] = xroot
rank[xroot] += 1
def countDisjointSubgraphs(N, edges):
parent = [i for i in range(N)]
rank = [0 for i in range(N)]
for edge in edges:
union(parent, rank, edge[0], edge[1])
unique_parents = set(find(parent, i) for i in range(N))
return len(unique_parents)
You can use the countDisjointSubgraphs function to solve the problem. The function takes the number of nodes N and a list of edges as input, and returns the number of disjoint subgraphs. Each edge is represented as a pair of integers (A, B).
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