add cc

Author: shellfly

cc.go

@@ -0,0 +1,46 @@
+package algo
+
+// CC ...
+type CC struct {
+	marked []bool
+	id     []int
+	count  int
+}
+
+// NewCC ...
+func NewCC(g *Graph) *CC {
+	cc := &CC{marked: make([]bool, g.V()), id: make([]int, g.V())}
+	for s := 0; s < g.V(); s++ {
+		if !cc.marked[s] {
+			cc.Dfs(g, s)
+			cc.count++
+		}
+	}
+	return cc
+}
+
+// Dfs ...
+func (cc *CC) Dfs(g *Graph, v int) {
+	cc.marked[v] = true
+	cc.id[v] = cc.count
+	for _, w := range g.Adj(v) {
+		if !cc.marked[w] {
+			cc.Dfs(g, w)
+		}
+	}
+}
+
+// Connected ...
+func (cc *CC) Connected(v, w int) bool {
+	return cc.id[v] == cc.id[w]
+}
+
+// ID ...
+func (cc *CC) ID(v int) int {
+	return cc.id[v]
+}
+
+// Count ...
+func (cc *CC) Count() int {
+	return cc.count
+}

cmd/cc/main.go

@@ -0,0 +1,61 @@
+/*
+  Execution:    go run cmd/cc/main.go filename.txt
+  Data files:   https://algs4.cs.princeton.edu/41graph/tinyG.txt
+                https://algs4.cs.princeton.edu/41graph/mediumG.txt
+                https://algs4.cs.princeton.edu/41graph/largeG.txt
+
+  Compute connected components using depth first search.
+  Runs in O(E + V) time.
+
+  % go run cmd/cc/main.go tinyG.txt
+  3 components
+  0 1 2 3 4 5 6
+  7 8
+  9 10 11 12
+
+  % pytyon cc.py mediumG.txt
+  1 components
+  0 1 2 3 4 5 6 7 8 9 10 ...
+
+  % go run cmd/cc/main.go largeG.txt
+  1 components
+  0 1 2 3 4 5 6 7 8 9 10 ...
+
+  Note: This implementation uses a recursive DFS. To avoid needing
+        a potentially very large stack size, replace with a non-recurisve
+        DFS ala NonrecursiveDFS.
+
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/shellfly/algo"
+	"github.com/shellfly/algo/stdin"
+)
+
+func main() {
+	graph := algo.NewGraph(stdin.NewIn(os.Args[1]))
+	cc := algo.NewCC(graph)
+
+	fmt.Println(cc.Count(), " components")
+	var components = []*algo.Bag{}
+	for i := 0; i < cc.Count(); i++ {
+		components = append(components, algo.NewBag())
+	}
+
+	for v := 0; v < graph.V(); v++ {
+		components[cc.ID(v)].Add(v)
+	}
+
+	for i := 0; i < cc.Count(); i++ {
+		for _, v := range components[i].Slice() {
+			fmt.Print(v, " ")
+		}
+		fmt.Println()
+	}
+
+}