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))
3.8
10
#include <iostream>
#include <vector>
#include <queue>
#include <functional>
#include <utility>
using namespace std;
const int MAX = 1e4 + 5;
typedef pair<long long, int> PII;
bool marked[MAX];
vector <PII> adj[MAX];
long long prim(int x)
{
priority_queue<PII, vector<PII>, greater<PII> > Q;
int y;
long long minimumCost = 0;
PII p;
Q.push(make_pair(0, x));
while(!Q.empty())
{
// Select the edge with minimum weight
p = Q.top();
Q.pop();
x = p.second;
// Checking for cycle
if(marked[x] == true)
continue;
minimumCost += p.first;
marked[x] = true;
for(int i = 0;i < adj[x].size();++i)
{
y = adj[x][i].second;
if(marked[y] == false)
Q.push(adj[x][i]);
}
}
return minimumCost;
}
int main()
{
int nodes, edges, x, y;
long long weight, minimumCost;
cin >> nodes >> edges;
for(int i = 0;i < edges;++i)
{
cin >> x >> y >> weight;
adj[x].push_back(make_pair(weight, y));
adj[y].push_back(make_pair(weight, x));
}
// Selecting 1 as the starting node
minimumCost = prim(1);
cout << minimumCost << endl;
return 0;
}
Thank you!
10
0
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