Add Minimum Spanning Tree in Go

archive/g/go/minimum-spanning-tree.go

@@ -0,0 +1,107 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const usage = `Usage: please provide a comma-separated list of integers`
+
+func main() {
+	if len(os.Args) != 2 {
+		printUsage()
+	}
+
+	matrix, errM := parseList(os.Args[1])
+
+	if errM != nil {
+		printUsage()
+	}
+
+	nFloat := math.Sqrt(float64(len(matrix)))
+	n := int(nFloat)
+	if nFloat != float64(n) || n == 0 {
+		printUsage()
+	}
+
+	cost, ok := primMST(matrix, n)
+	if !ok {
+		printUsage()
+	}
+
+	fmt.Println(cost)
+}
+
+func primMST(matrix []int, n int) (int, bool) {
+	if n == 0 {
+		return 0, true
+	}
+
+	inMST := make([]bool, n)
+	minWeights := make([]int, n)
+	for i := range minWeights {
+		minWeights[i] = math.MaxInt32
+	}
+
+	minWeights[0] = 0
+	totalWeight := 0
+	nodesInTree := 0
+
+	for i := 0; i < n; i++ {
+		u := -1
+		minVal := math.MaxInt32
+
+		for v := 0; v < n; v++ {
+			if !inMST[v] && minWeights[v] < minVal {
+				minVal = minWeights[v]
+				u = v
+			}
+		}
+
+		if u == -1 {
+			break
+		}
+
+		inMST[u] = true
+		totalWeight += minVal
+		nodesInTree++
+
+		for v := 0; v < n; v++ {
+			weight := matrix[u*n+v]
+			if weight > 0 && !inMST[v] && weight < minWeights[v] {
+				minWeights[v] = weight
+			}
+		}
+	}
+
+	if nodesInTree != n {
+		return 0, false
+	}
+
+	return totalWeight, true
+}
+
+func parseList(input string) ([]int, error) {
+	if strings.TrimSpace(input) == "" {
+		return nil, fmt.Errorf("empty input")
+	}
+
+	parts := strings.Split(input, ",")
+	nums := make([]int, 0, len(parts))
+	for _, p := range parts {
+		val, err := strconv.Atoi(strings.TrimSpace(p))
+		if err != nil {
+			return nil, err
+		}
+		nums = append(nums, val)
+	}
+	return nums, nil
+}
+
+func printUsage() {
+	fmt.Println(usage)
+	os.Exit(1)
+}