Lab 5

README.md

@@ -1,24 +1,3 @@
-# Lab-1 
+# Lab 5 - Kruskal's algorithm
 
-## Task
-Implement a sorting algorithm - HeapSort(ascending/descending)
-
-## Result output
-- Algorithm's name
-- Execution time
-- Counters: swaps, comparisons
-- Sorting result
-
-## Code must be covered with tests
-- sort the input array
-- sort in ascending order of sorted array in ascending order
-- sort in descending order of sorted array in ascending order
-- sort in ascending order of sorted array in descending order
-- sort in descending order of sorted array in descending order
-
-## How to run
-- 'cd' into folder where you want to store this repository
-- Clone this repository with command 'git clone https://github.com/yeldmitrenko/Algorithms_Labs.git'
-- Choose branch lab_1 with command 'git checkout lab_1'
-- Go into folder with files with command 'cd Algorithms_Labs'
-- run command 'python main.py'
+### Kruskal's algorithm for finding a minimum spanning tree

kruskal's.py

@@ -0,0 +1,78 @@
+from typing import List
+
+
+class Edge:
+    def __init__(self, start_vertex, end_vertex, weight):
+        self.start_vertex = start_vertex
+        self.end_vertex = end_vertex
+        self.weight = weight
+
+
+class Graph:
+    def __init__(self, nodes_number):
+        self.nodes_number = nodes_number
+        self.edge_list = List[Edge]
+        self.mst = []
+        self.rank = 0
+        self.parent = self
+
+    def add(self, listkk: list[Edge]):
+        self.edge_list = listkk
+
+    def find_root(self):
+        if self.parent is not self:
+            self.parent = self.parent.find_root()
+        return self.parent
+
+    def union_sets(self, other):
+        first_set_root = self.find_root()
+        second_set_root = other.find_root()
+        if first_set_root is second_set_root:
+            return
+        if first_set_root.rank < second_set_root.rank:
+            first_set_root.parent = second_set_root
+        elif first_set_root.rank > second_set_root.rank:
+            second_set_root.parent = first_set_root
+        else:
+            second_set_root.parent = first_set_root
+            first_set_root.rank += 1
+
+    def kruskal_mst(self):
+        nodes_not_unique = []
+        for edge in sorted(self.edge_list, key=lambda Edge: Edge.weight):
+            nodes_not_unique.append(edge.start_vertex)
+            nodes_not_unique.append(edge.end_vertex)
+
+        nodes = list(set(nodes_not_unique))
+
+        result = dict((node, Graph(node)) for node in nodes)
+        print(result)
+        for edge in sorted(self.edge_list, key=lambda Edge: Edge.weight):
+
+            start = result[edge.start_vertex].find_root()
+            end = result[edge.end_vertex].find_root()
+
+            if start is not end:
+                self.mst.append(edge)
+                start.union_sets(end)
+
+
+if __name__ == '__main__':
+    nodes_number = 7
+    e1 = Edge(1, 2, 7)
+    e2 = Edge(1, 4, 5)
+    e3 = Edge(3, 5, 5)
+    e4 = Edge(2, 5, 7)
+    e5 = Edge(5, 7, 9)
+    e6 = Edge(4, 6, 6)
+
+    graph = Graph(nodes_number)
+    graph.add([e1, e2, e3, e4, e5, e6])
+    graph.kruskal_mst()
+
+    print("\nEdges of minimum spanning tree in graph :", end=' ')
+    cost = 0
+    for edge in graph.mst:
+        print("[" + str(edge.start_vertex) + "-" + str(edge.end_vertex) + "](" + str(edge.weight) + ")", end=' ')
+        cost += edge.weight
+    print("\nCost of minimum spanning tree : " + str(cost))