prim python code example

Example 1: c program for prims algorithm

#include<stdio.h>
#include<conio.h>
int a,b,u,v,n,i,j,ne=1;
int visited[10]= {	0},min,mincost=0,cost[10][10];
void main() {	
clrscr();	
printf("\n Enter the number of nodes:");	
scanf("%d",&n);	
printf("\n Enter the adjacency matrix:\n");	
for (i=1;i<=n;i++)	  
    for (j=1;j<=n;j++) {		
      scanf("%d",&cost[i][j]);		
      if(cost[i][j]==0)		    
      cost[i][j]=999;	
      }	
    visited[1]=1;	
    printf("\n");	
    while(ne<n) {		
      for (i=1,min=999;i<=n;i++)		  
        for (j=1;j<=n;j++)		    
          if(cost[i][j]<min)		     
          if(visited[i]!=0) {			
          min=cost[i][j];			
          a=u=i;			
          b=v=j;		
          }		
          if(visited[u]==0 || visited[v]==0) 
          {			
            printf("\n Edge %d:(%d %d) cost:%d",ne++,a,b,min);
            mincost+=min;			
            visited[b]=1;		
            }		
          cost[a][b]=cost[b][a]=999;	
          }	
          printf("\n Minimun cost=%d",mincost);
          getch();
}

Example 2: prim's algorithm python

def empty_graph(n):
    res = []
    for i in range(n):
        res.append([0]*n)
    return res
def convert(graph):
    matrix = []
    for i in range(len(graph)): 
        matrix.append([0]*len(graph))
        for j in graph[i]:
            matrix[i][j] = 1
    return matrix
def prims_algo(graph):
    graph1 = convert(graph)
    n = len(graph1)
    tree = empty_graph(n)
    con =[0]
    while len(con) < n :
        found = False
        for i in con:
            for j in range(n):
                if j not in con and graph1[i][j] == 1:
                    tree[i][j] =1
                    tree[j][i] =1
                    con += [j]
                    found  = True
                    break
            if found :
                break
    return tree
matrix = [[0, 1, 1, 1, 0, 1, 1, 0, 0],
          [1, 0, 0, 1, 0, 0, 1, 1, 0],
          [1, 0, 0, 1, 0, 0, 0, 0, 0],
          [1, 1, 1, 0, 1, 0, 0, 0, 0],
          [0, 0, 0, 1, 0, 1, 0, 0, 1],
          [1, 0, 0, 0, 1, 0, 0, 0, 1],
          [1, 1, 0, 0, 0, 0, 0, 0, 0],
          [0, 1, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 1, 1, 0, 0, 0]]

lst = [[1,2,3,5,6],[0,3,6,7],[0,3],[0,1,2,4],[3,5,8],[0,4,8],[0,1],[1],[4,5]]
print("From graph to spanning tree:\n")
print(prims_algo(lst))

Example 3: prims minimum spanning tree

import math
def empty_tree (n):
    lst = []
    for i in range(n):
        lst.append([0]*n)
    return lst
def min_extension (con,graph,n):
    min_weight = math.inf
    for i in con:
        for j in range(n):
            if j not in con and 0 < graph[i][j] < min_weight:
                min_weight = graph[i][j]
                v,w = i,j
    return v,w
            
def min_span(graph):
    con = [0]
    n = len(graph)
    tree = empty_tree(n)
    while len(con) < n :
        i ,j  = min_extension(con,graph,n)
        tree[i][j],tree[j][i] = graph[i][j], graph[j][i]
        con += [j]
    return tree

def find_weight_of_edges(graph):
    tree = min_span(graph)
    lst = []
    lst1 = []
    x = 0
    for i in tree:
        lst += i 
    for i in lst:
        if i not in lst1:
            lst1.append(i)
            x += i
    return x

graph = [[0,1,0,0,0,0,0,0,0],
         [1,0,3,4,0,3,0,0,0],
         [0,3,0,0,0,4,0,0,0],
         [0,4,0,0,2,9,1,0,0],
         [0,0,0,2,0,6,0,0,0],
         [0,3,4,9,6,0,0,0,6],
         [0,0,0,1,0,0,0,2,8],
         [0,0,0,0,0,0,2,0,3],
         [0,0,0,0,0,6,8,3,0]]
graph1 = [[0,3,5,0,0,6],
          [3,0,4,1,0,0],
          [5,4,0,4,5,2],
          [0,1,4,0,6,0],
          [0,0,5,6,0,8],
          [6,0,2,0,8,0]]
print(min_span(graph1))
print("Total weight of the tree is: " + str(find_weight_of_edges(graph1)))