From 3e15f2b673f4d2a735bd3146120e8b0648366483 Mon Sep 17 00:00:00 2001
From: Trived-K <117757559+Trived-K@users.noreply.github.com>
Date: Sun, 4 Dec 2022 13:27:20 +0530
Subject: [PATCH] Added Python implementation for kruskal's algorithm

---
 classicalAlgos/kruskalsAlgorithm/kruskals.py | 67 ++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 classicalAlgos/kruskalsAlgorithm/kruskals.py

diff --git a/classicalAlgos/kruskalsAlgorithm/kruskals.py b/classicalAlgos/kruskalsAlgorithm/kruskals.py
new file mode 100644
index 0000000..81ed083
--- /dev/null
+++ b/classicalAlgos/kruskalsAlgorithm/kruskals.py
@@ -0,0 +1,67 @@
+#Use disjoint union set structure to check if two nodes belong to same connected component
+class Union_Set:
+    def __init__(self,numberOfNodes):
+        self.numberOfNodes = numberOfNodes
+        #Initially Each node represents it's own connected component of size 1
+        self.parent = [i for i in range(numberOfNodes)]
+        self.setSize = [1 for i in range(numberOfNodes)]
+    def find_parent(self,nodeV):
+        if self.parent[nodeV] == nodeV:
+            return nodeV
+        self.parent[nodeV] = self.find_parent(self.parent[nodeV])
+        return self.parent[nodeV]
+    #Returns true if two nodes does not belong to the same connected component
+    def Merge_Sets(self,nodeA,nodeB):
+        nodeA = self.find_parent(nodeA)
+        nodeB = self.find_parent(nodeB)
+        if nodeA != nodeB:
+            if self.setSize[nodeA] > self.setSize[nodeB]:
+                self.parent[nodeB] = nodeA
+                self.setSize[nodeA] += self.setSize[nodeB]
+                print(nodeA, nodeB)
+            else:
+                self.parent[nodeA] = nodeB
+                self.setSize[nodeB] += self.setSize[nodeA]
+                print(nodeB, nodeA)
+            return True
+        return False
+
+class Graph:
+    def __init__(self,numberOfNodes):
+        self.numberOfNodes = numberOfNodes
+        self.graph = []
+    def add_edge(self,nodeA,nodeB,edgeWeight):
+        #Add an undirected weighted edge between node A and node B
+        self.graph.append([nodeA,nodeB,edgeWeight])
+    def Krsukals(self):
+        self.graph = sorted(self.graph,key=lambda edge : edge[2])
+        dsu = Union_Set(self.numberOfNodes)
+        numberOfEdges = len(self.graph)
+        minMstWeight = 0
+        mstEdges = []
+        for edge in self.graph:
+            #Adds this edge to list of edges in minimum spanning tree if these nodes belong to different connected components
+            if dsu.Merge_Sets(edge[0],edge[1]):
+                mstEdges.append(edge)
+                minMstWeight += edge[2]
+        print(minMstWeight)
+        #Prints all the edges that belong to the miniumum spanning tree
+        for edge in mstEdges:
+            print("{" , edge[0], ",", edge[1],"} W:",edge[2])
+
+g = Graph(9)
+g.add_edge(0, 1, 7)
+g.add_edge(0, 7, 7)
+g.add_edge(1, 7, 11)
+g.add_edge(1, 2, 4)
+g.add_edge(7, 8, 4)
+g.add_edge(6, 7, 6)
+g.add_edge(2, 8, 3)
+g.add_edge(6, 8, 3)
+g.add_edge(2, 3, 2)
+g.add_edge(2, 5, 2)
+g.add_edge(5, 6, 1)
+g.add_edge(3, 5, 4)
+g.add_edge(3, 4, 1)
+g.add_edge(4, 5, 11)
+g.Krsukals()