Data commit

Task/Kosaraju/Go/kosaraju.go

@@ -0,0 +1,60 @@
+package main
+
+import "fmt"
+
+var g = [][]int{
+    0: {1},
+    1: {2},
+    2: {0},
+    3: {1, 2, 4},
+    4: {3, 5},
+    5: {2, 6},
+    6: {5},
+    7: {4, 6, 7},
+}
+
+func main() {
+    fmt.Println(kosaraju(g))
+}
+
+func kosaraju(g [][]int) []int {
+    // 1. For each vertex u of the graph, mark u as unvisited. Let L be empty.
+    vis := make([]bool, len(g))
+    L := make([]int, len(g))
+    x := len(L)                // index for filling L in reverse order
+    t := make([][]int, len(g)) // transpose graph
+    // 2. recursive subroutine:
+    var Visit func(int)
+    Visit = func(u int) {
+        if !vis[u] {
+            vis[u] = true
+            for _, v := range g[u] {
+                Visit(v)
+                t[v] = append(t[v], u) // construct transpose
+            }
+            x--
+            L[x] = u
+        }
+    }
+    // 2. For each vertex u of the graph do Visit(u)
+    for u := range g {
+        Visit(u)
+    }
+    c := make([]int, len(g)) // result, the component assignment
+    // 3: recursive subroutine:
+    var Assign func(int, int)
+    Assign = func(u, root int) {
+        if vis[u] { // repurpose vis to mean "unassigned"
+            vis[u] = false
+            c[u] = root
+            for _, v := range t[u] {
+                Assign(v, root)
+            }
+        }
+    }
+    // 3: For each element u of L in order, do Assign(u,u)
+    for _, u := range L {
+        Assign(u, u)
+    }
+    return c
+}