Added Boruvka's algorithm under greedy for issue#60

greedy/boruvka's_graphMST/boruvka's_algorithm.go

@@ -0,0 +1,191 @@
+package main
+
+/*
+Boruvka's Algorithm:
+	1) Initialize all vertices as individual components.
+	2) Initialize MST = [] empty.
+	3) While there are more than one component do:
+		For each component:
+			i. Find closest weight edge that connect the component to another.
+			ii. Add this edge to the MST if not already added.
+	4) Return MST.
+*/
+
+/*
+s - Source
+d - Destination
+w - Weight
+v - Vertex
+e - Edge
+g - Graph
+*/
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// Stores the information about one edge
+type Edge struct {
+	s, d, w int // Source, Destination, Weight
+}
+
+// Stores the vertices and edge list of the graph
+type Graph struct {
+	v int
+	e []Edge
+}
+
+// Creating a graph
+func create_graph(v int) *Graph {
+	return &Graph{v: v, e: []Edge{}}
+}
+
+// Adding an edge to the graph
+func (g *Graph) add_edge(s, d, w int) {
+	g.e = append(g.e, Edge{s: s, d: d, w: w})
+}
+
+// Find the root of a given vertex (Used to identify the component)
+func (g *Graph) find_root(component []int, v int) int {
+	root := v
+	for component[root] != root {
+		root = component[root]
+	}
+	for v != root {
+		parent := component[v]
+		component[v] = root
+		v = parent
+	}
+	return root
+}
+
+func (g *Graph) Boruvka_algo() []Edge {
+
+	// Initialize all vertex as its own component
+	component := make([]int, g.v)
+	for i := 0; i < g.v; i++ {
+		component[i] = i
+	}
+
+	// Initialize MST = [] empty
+	mst := []Edge{}
+	components := g.v
+
+	// While there are more than one component do:
+	for components > 1 {
+		// For each component:
+		shortest := make([]*Edge, g.v)
+
+		// Find the shortest edge that connects the component to another
+		for _, edge := range g.e {
+			s_root := g.find_root(component, edge.s)
+			d_root := g.find_root(component, edge.d)
+
+			// If it is 2 different components
+			if s_root != d_root {
+				if shortest[s_root] == nil || shortest[s_root].w > edge.w {
+					e := edge
+					shortest[s_root] = &e
+				}
+
+				if shortest[d_root] == nil || shortest[d_root].w > edge.w {
+					e := edge
+					shortest[d_root] = &e
+				}
+			}
+		}
+
+		// Add this edge to the MST if not already added
+		for i := 0; i < g.v; i++ {
+			if shortest[i] != nil {
+				s_root := g.find_root(component, shortest[i].s)
+				d_root := g.find_root(component, shortest[i].d)
+				edge := shortest[i]
+
+				// Merging components and adding edge to MST
+				if s_root != d_root {
+					mst = append(mst, *edge)
+					root1 := g.find_root(component, s_root)
+					root2 := g.find_root(component, d_root)
+					component[root1] = root2
+					components--
+				}
+			}
+		}
+	}
+	// Return MST
+	return mst
+}
+
+func main() {
+	read := bufio.NewReader(os.Stdin)
+
+	// Input the number of vertices and edges
+	fmt.Print("Enter number of vertices and edges: ")
+	input, _ := read.ReadString('\n')
+	input = strings.TrimSpace(input)
+	v_e := strings.Split(input, " ")
+	v, _ := strconv.Atoi(v_e[0])
+	e, _ := strconv.Atoi(v_e[1])
+
+	// Create the graph
+	graph := create_graph(v)
+
+	// Getting input for edges
+	fmt.Println("Enter edge info:")
+	for i := 0; i < e; i++ {
+		edge, _ := read.ReadString('\n')
+		edge = strings.TrimSpace(edge)
+		edge_lis := strings.Split(edge, " ")
+		s, _ := strconv.Atoi(edge_lis[0])
+		d, _ := strconv.Atoi(edge_lis[1])
+		w, _ := strconv.Atoi(edge_lis[2])
+
+		graph.add_edge(s, d, w) // Inserting into graph
+	}
+
+	// Finding the MST
+	mst := graph.Boruvka_algo()
+
+	// Printing the MST
+	fmt.Println("Edges in the Minimum Spanning Tree:")
+	total_weight := 0
+	for _, edge := range mst {
+		fmt.Printf("%d,%d = %d\n", edge.s, edge.d, edge.w)
+		total_weight += edge.w
+	}
+	fmt.Printf("Total weight: %d\n", total_weight)
+}
+
+/* Test case:
+Enter number of vertices and edges: 9 14
+Enter edge info:
+0 1 4
+1 2 8
+2 3 7
+3 4 9
+4 5 10
+5 6 2
+6 7 1
+7 0 8
+1 7 11
+3 5 14
+7 8 7
+8 6 2
+2 8 2
+2 5 4
+Output:
+Edges in the Minimum Spanning Tree:
+0,1 = 4
+2,8 = 2
+2,3 = 7
+3,4 = 9
+5,6 = 2
+6,7 = 1
+8,6 = 2
+1,2 = 8
+Total weight: 35 */