<｜begin▁of▁sentence｜>### Instruction:
{'Description': 'Given a directed acyclic graph with edge set [(0, 1), (0, 3), (1, 2)], compute the lowest common ancestor for all pairs of nodes, and for specific pairs (1, 2) and (2, 3).', 'Graph': 'The graph is a directed acyclic graph (DAG) with nodes [0, 1, 2, 3] and edges connecting them as specified by the tuples in the edge set.', 'Problem': 'The code should output the lowest common ancestor for all pairs of nodes within the graph and for the specific pairs of nodes provided.'}
### Response:
import networkx as nx

# Create a directed acyclic graph (DAG)
G = nx.DiGraph([(0, 1), (0, 3), (1, 2)])

# Compute the lowest common ancestor for all pairs
# Convert the generator to a dictionary for better visualization
lca_all_pairs = dict(nx.all_pairs_lowest_common_ancestor(G))

print('All pairs lowest common ancestor:')
print(lca_all_pairs)

# Now compute the LCA for specific pairs
specific_pairs = [(1, 2), (2, 3)]
lca_specific_pairs = dict(nx.all_pairs_lowest_common_ancestor(G, pairs=specific_pairs))

print('\nSpecific pairs lowest common ancestor:')
print(lca_specific_pairs)
<|EOT|>
