Prim算法是一种用于求解最小生成树(MST)的贪心算法。它的基本思想是:从一个顶点出发,每次找到最近的顶点,并将其加入到最小生成树中,直到所有的顶点都被加入到最小生成树中。
Prim算法是一种用于求解最小生成树(MST)的贪心算法。它的基本思想是:从一个顶点出发,每次找到最近的顶点,并将其加入到最小生成树中,直到所有的顶点都被加入到最小生成树中。
下面是使用Python实现Prim算法的代码:
# Python program for Prim's Minimum Spanning Tree (MST) algorithm.
# The program is for adjacency matrix representation of the graph
import sys # Library for INT_MAX
cl Graph():
def __init__(self, vertices):
self.V = vertices
self.graph = [[0 for column in range(vertices)]
for row in range(vertices)]
# A utility function to print the constructed MST stored in parent[]
def printMST(self, parent):
print("Edge \tWeight")
for i in range(1, self.V):
print(parent[i], "-", i, "\t", self.graph[i][ parent[i] ] )
# A utility function to find the vertex with
# minimum distance value, from the set of vertices
# not yet included in shortest path tree
def minKey(self, key, mstSet):
# Initilaize min value
min = sys.maxsize
for v in range(self.V):
if key[v] < min and mstSet[v] == False:
min = key[v]
min_index = v
return min_index
# Function to construct and print MST for a graph
# represented using adjacency matrix representation
def primMST(self):
# Key values used to pick minimum weight edge in cut
key = [sys.maxsize] * self.V
parent = [None] * self.V # Array to store constructed MST
# Make key 0 so that this vertex is picked as first vertex
key[0] = 0
mstSet = [False] * self.V
parent[0] = -1 # First node is always the root of
for cout in range(self.V):
# Pick the minimum distance vertex from
# the set of vertices not yet processed.
# u is always equal to src in first iteration
u = self.minKey(key, mstSet)
# Put the minimum distance vertex in
# the shortest path tree
mstSet[u] = True
# Update dist value of the adjacent vertices
# of the picked vertex only if the current
# distance is greater than new distance and
# the vertex in not in the shotest path tree
for v in range(self.V):
# graph[u][v] is non zero only for adjacent vertices of m
# mstSet[v] is false for vertices not yet included in MST
# Update the key only if graph[u][v] is smaller than key[v]
if self.graph[u][v] > 0 and mstSet[v] == False and key[v] > self.graph[u][v]:
key[v] = self.graph[u][v]
parent[v] = u
self.printMST(parent)
g = Graph(5)
g.graph = [ [0, 2, 0, 6, 0],
[2, 0, 3,
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