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class Edge:
def __init__(self, u, v):
self.u = u
self.v = v
def opposite(self, x):
if x == self.u:
return self.v
elif x == self.v:
return self.u
else:
return None
class Graph:
def __init__(self, n):
self.adj = {i: [] for i in range(1,n+1)}
def add_edge(self, u, v):
e = Edge(u, v)
self.adj[u].append(e)
self.adj[v].append(e)
def incident_edges(self, u):
return self.adj[u]
def vertices(self):
return self.adj.keys()
def DFS(g, u, forest):
for e in g.incident_edges(u):
v = e.opposite(u)
if v not in forest:
forest[v] = e
DFS(g, v, forest)
def DFS_complete(g, start):
forest = {}
forest[start] = None
DFS(g, start, forest)
for u in g.vertices():
if u not in forest:
forest[u] = None
DFS(g, u, forest)
return forest
print("\tDepth First Search Tree Traversal\n")
n = int(input("Enter number of vertices: "))
m = int(input("Enter number of edges: "))
g = Graph(n)
print("Give vertex numbers from 1 to ", n)
print("Enter edges (u v):")
for _ in range(m):
u, v = map(int, input().split())
g.add_edge(u, v)
start = int(input("Enter starting vertex: "))
forest = DFS_complete(g, start)
print("\nDFS Tree (vertex : discovered from)")
for v in forest:
if forest[v] is None:
print(f"{v} : None (root)")
else:
parent = forest[v].opposite(v)
print(f"{v} : discovered from {parent}") |