Initial data commit

Task/Tarjan/Go/tarjan.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+    "fmt"
+    "math/big"
+)
+
+// (same data as zkl example)
+var g = [][]int{
+    0: {1},
+    2: {0},
+    5: {2, 6},
+    6: {5},
+    1: {2},
+    3: {1, 2, 4},
+    4: {5, 3},
+    7: {4, 7, 6},
+}
+
+func main() {
+    tarjan(g, func(c []int) { fmt.Println(c) })
+}
+
+// the function calls the emit argument for each component identified.
+// each component is a list of nodes.
+func tarjan(g [][]int, emit func([]int)) {
+    var indexed, stacked big.Int
+    index := make([]int, len(g))
+    lowlink := make([]int, len(g))
+    x := 0
+    var S []int
+    var sc func(int) bool
+    sc = func(n int) bool {
+        index[n] = x
+        indexed.SetBit(&indexed, n, 1)
+        lowlink[n] = x
+        x++
+        S = append(S, n)
+        stacked.SetBit(&stacked, n, 1)
+        for _, nb := range g[n] {
+            if indexed.Bit(nb) == 0 {
+                if !sc(nb) {
+                    return false
+                }
+                if lowlink[nb] < lowlink[n] {
+                    lowlink[n] = lowlink[nb]
+                }
+            } else if stacked.Bit(nb) == 1 {
+                if index[nb] < lowlink[n] {
+                    lowlink[n] = index[nb]
+                }
+            }
+        }
+        if lowlink[n] == index[n] {
+            var c []int
+            for {
+                last := len(S) - 1
+                w := S[last]
+                S = S[:last]
+                stacked.SetBit(&stacked, w, 0)
+                c = append(c, w)
+                if w == n {
+                    emit(c)
+                    break
+                }
+            }
+        }
+        return true
+    }
+    for n := range g {
+        if indexed.Bit(n) == 0 && !sc(n) {
+            return
+        }
+    }
+}