prim algorithm - minimum spanning tree

First of all we are here to tell us about prim algorithms, data structures, I remember the first university finished minimum spanning tree, tell the shortest path problem is a compulsory study section.

prim global minimum spanning tree algorithm to find weighting FIG communication inside. It is a greedy algorithm.

Here are two pictures I steal oh. Hee hee hee

 

algorithm:

1, input: a weighted FIG communication, set V of vertices, a set E of edges.

Input representation of a two-dimensional matrix (Note: there is no set length of a side of the communication MAX): as

 

Import SYS 
MAX = sys.maxsize # set to infinity

The matrix is ​​expressed as:

primgraph = 
            [[MAX, 6, 1, 5, MAX, MAX],
             [6, MAX, 5, MAX, 3, MAX],
             [1, 5, MAX, 5, 6, 4],
             [5, MAX, 5, MAX, MAX,2],
             [MAX, 3, 6, MAX, MAX, 6],
             [MAX, MAX, 4, 2, 6, MAX]]

chararray = ['A', 'B', 'C', 'D', 'E', 'F']        

Initialization value: The total cost of the minimum spanning tree --lowcost, open up an array of storage node minimum spanning tree

charlist.append (chararray [0])   # store a first initial node 
Lowcost = [] 
lowcost.append ( -1)   # first storage node is set to 0 
SUM is the total weight of the minimum spanning tree weight

Add the remaining inter initialization initialization point A lowcost

for i in range(1, n):
    lowcost.append(primgraph[0][i])

He began tentatively on the edge of victory

Start the next iteration

for _ in Range (. 1, n-):                # traversing nodes other than the point A 
    min = MAX                        # per find the smallest edge, min for comparing 
    minid 0 =                        # per minid used to store the lowest node index 
    for J in Range (. 1, n-):            # find the minimum weight junction, and! = -1 is not favorite of the emperor 
        IF Lowcost [J] = -1! And Lowcost [J] < min: 
            min = Lowcost [J] 
            minid = J 
    charlist.append (chararray [minid])   # minimum spanning added shortest path that node 
    SUM = SUM + min                       #Total weight plus the weight of the remaining nodes in the shortest weight 
    Lowcost [minid] -1 =                 # of the node just been patronize the shortest path, past the formula 
    for J in Range (. 1, n-):               # update list favorite of the most critical part! ! ! ! 
        IF Lowcost [J] = -1! and Lowcost [J]> primgraph [minid] [J]:
         # all nodes already patronize, patronize from the node has to find the shortest path, updated 
            lowcost [j] = primgraph [ mini