search: combine reconstruction recursions

I don't think the same work improves readability for the iterative case.

search/shortest.go

@@ -226,62 +226,48 @@ func (p ShortestPaths) AllBetween(u, v graph.Node) (paths [][]graph.Node, weight
 		return nil, math.Inf(1)
 	}
 
-	switch {
-	case p.forward:
-		// Do forward path reconstruction.
-		seen := make([]bool, len(p.nodes))
-		paths = p.allBetweenForward(from, to, seen, []graph.Node{p.nodes[from]}, nil)
-
-	default:
-		// Do reverse path reconstruction.
-		seen := make([]bool, len(p.nodes))
-		paths = p.allBetweenReverse(from, to, seen, []graph.Node{p.nodes[to]}, nil)
+	var n graph.Node
+	if p.forward {
+		n = u
+	} else {
+		n = v
 	}
+	seen := make([]bool, len(p.nodes))
+	paths = p.allBetween(from, to, seen, []graph.Node{n}, nil)
 
 	return paths, p.dist.At(from, to)
 }
 
-func (p ShortestPaths) allBetweenForward(from, to int, seen []bool, path []graph.Node, paths [][]graph.Node) [][]graph.Node {
-	seen[from] = true
-	if from == to {
-		if path == nil {
-			return paths
-		}
-		return append(paths, path)
+func (p ShortestPaths) allBetween(from, to int, seen []bool, path []graph.Node, paths [][]graph.Node) [][]graph.Node {
+	if p.forward {
+		seen[from] = true
+	} else {
+		seen[to] = true
 	}
-	first := true
-	for _, from := range p.at(from, to) {
-		if seen[from] {
-			continue
-		}
-		if first {
-			path = append([]graph.Node(nil), path...)
-			first = false
-		}
-		paths = p.allBetweenForward(from, to, append([]bool(nil), seen...), append(path, p.nodes[from]), paths)
-	}
-	return paths
-}
-
-func (p ShortestPaths) allBetweenReverse(from, to int, seen []bool, path []graph.Node, paths [][]graph.Node) [][]graph.Node {
-	seen[to] = true
 	if from == to {
 		if path == nil {
 			return paths
 		}
-		reverse(path)
+		if !p.forward {
+			reverse(path)
+		}
 		return append(paths, path)
 	}
 	first := true
-	for _, to := range p.at(from, to) {
-		if seen[to] {
+	for _, n := range p.at(from, to) {
+		if seen[n] {
 			continue
 		}
 		if first {
 			path = append([]graph.Node(nil), path...)
 			first = false
 		}
-		paths = p.allBetweenReverse(from, to, append([]bool(nil), seen...), append(path, p.nodes[to]), paths)
+		if p.forward {
+			from = n
+		} else {
+			to = n
+		}
+		paths = p.allBetween(from, to, append([]bool(nil), seen...), append(path, p.nodes[n]), paths)
 	}
 	return paths
 }