/
kruskal.go
114 lines (93 loc) · 2.01 KB
/
kruskal.go
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package main
import (
"fmt"
"container/heap"
"github.com/echinmay/unionfind"
"bufio"
"flag"
"strconv"
"strings"
"os"
"log"
)
type Edge struct {
source int
peer int
weight int
}
type EdgesSorted []*Edge
func (ed EdgesSorted) Len() int {
return len(ed)
}
func (ed EdgesSorted) Less(i, j int) bool {
return ed[i].weight < ed[j].weight
}
func (ed EdgesSorted) Swap(i, j int) {
ed[i], ed[j] = ed[j], ed[i]
}
func (ed *EdgesSorted) Push(x interface{}) {
edge := x.(*Edge)
*ed = append(*ed, edge)
}
func (ed *EdgesSorted) Pop() interface{} {
old := *ed
n := len(old)
item := old[n-1]
*ed = old[0:n-1]
return item
}
func main() {
var inputfile string
// Get the input file if sent as command line argument or use default
flag.StringVar(&inputfile, "input", "input.txt", "<NAME OF INPUT FILE>")
flag.Parse()
file, err := os.Open(inputfile)
if err != nil {
log.Fatal(err)
}
defer file.Close()
scanner := bufio.NewScanner(file)
scanner.Scan()
line := scanner.Text()
inputs := strings.Fields(line)
numnodes, _ := strconv.Atoi(inputs[0])
uf := unionfind.New(numnodes)
edges := make(EdgesSorted, 0)
heap.Init(&edges)
for scanner.Scan() {
line = scanner.Text()
if len(line) == 0 {
continue
}
inputs = strings.Fields(line)
source, err := strconv.Atoi(inputs[0])
if err != nil {
log.Fatal("Wrong format")
}
destination, err := strconv.Atoi(inputs[1])
if err != nil {
log.Fatal("Wrong format")
}
weight, err := strconv.Atoi(inputs[2])
if err != nil {
log.Fatal("Wrong format")
}
heap.Push(&edges, &Edge{source, destination, weight})
}
MST := make([]*Edge, 0)
for edges.Len() > 0 && uf.GetNumClusters() > 1 {
edgeout := heap.Pop(&edges).(*Edge)
if uf.Connected(edgeout.source, edgeout.peer) != true {
uf.Union(edgeout.source, edgeout.peer)
MST = append(MST, edgeout)
}
}
if uf.GetNumClusters() > 1 {
fmt.Println("Could not get Minimum Spanning Tree")
} else {
for x := range MST {
fmt.Println("Edges in MST")
fmt.Println(*MST[x])
}
}
}