wip rbtree

1 files changed, 134 insertions, 0 deletions

diff --git a/pkg/rbtree/rbtree_test.go b/pkg/rbtree/rbtree_test.go
new file mode 100644
index 0000000..6c49127
--- /dev/null
+++ b/pkg/rbtree/rbtree_test.go
@@ -0,0 +1,134 @@
+package rbtree
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/exp/constraints"
+)
+
+func printTree[K constraints.Ordered, V any](t *testing.T, tree *Tree[K, V]) {
+	fmtBareNode := func(node *Node[V]) string {
+		if node == nil {
+			return "nil"
+		}
+		if node.Color == Red {
+			return fmt.Sprintf("R(%v)", node.Value)
+		} else {
+			return fmt.Sprintf("B(%v)", node.Value)
+		}
+	}
+	addIndent := func(indent string, lines []string) []string {
+		ret := make([]string, 0, len(lines))
+		for _, line := range lines {
+			ret = append(ret, indent+line)
+		}
+		return ret
+	}
+	var fmtNode func(node *Node[V]) []string
+	fmtNode = func(node *Node[V]) []string {
+		if node == nil {
+			return []string{"nil"}
+		}
+		ret := addIndent("    ", fmtNode(node.Right))
+		ret = append(ret, fmtBareNode(node))
+		ret = append(ret, addIndent("    ", fmtNode(node.Left))...)
+		return ret
+	}
+	t.Log("\n" + strings.Join(fmtNode(tree.root), "\n"))
+}
+
+func checkTree[K constraints.Ordered, V any](t *testing.T, tree *Tree[K, V]) {
+	// 1. Every node is either red or black
+
+	// 2. The root is black.
+	assert.Equal(t, Black, tree.root.getColor())
+
+	// 3. Every nil is black.
+
+	// 4. If a node is red, then both its children are black.
+	tree.Walk(func(node *Node[V]) {
+		if node.getColor() == Red {
+			assert.Equal(t, Black, node.Left.getColor())
+			assert.Equal(t, Black, node.Right.getColor())
+		}
+	})
+
+	// 5. For each node, all simple paths from the node to
+	//    descendent leaves contain the same number of black
+	//    nodes.
+	var walkCnt func(node *Node[V], cnt int, leafFn func(int))
+	walkCnt = func(node *Node[V], cnt int, leafFn func(int)) {
+		if node.getColor() == Black {
+			cnt++
+		}
+		if node == nil {
+			leafFn(cnt)
+			return
+		}
+		walkCnt(node.Left, cnt, leafFn)
+		walkCnt(node.Right, cnt, leafFn)
+	}
+	tree.Walk(func(node *Node[V]) {
+		var cnts []int
+		walkCnt(node, 0, func(cnt int) {
+			cnts = append(cnts, cnt)
+		})
+		for i := range cnts {
+			if cnts[0] != cnts[i] {
+				if !assert.Truef(t, false, "node %v: not all leafs have same black-count: %v", node.Value, cnts) {
+					printTree(t, tree)
+				}
+			}
+		}
+	})
+}
+
+func FuzzTree(f *testing.F) {
+	Ins := uint8(0b0100_0000)
+	Del := uint8(0)
+
+	f.Add([]uint8{})
+	f.Add([]uint8{Ins | 5, Del | 5})
+	f.Add([]uint8{Ins | 5, Del | 6})
+	f.Add([]uint8{Del | 6})
+
+	f.Add([]uint8{ // CLRS Figure 14.4
+		Ins | 1,
+		Ins | 2,
+		Ins | 5,
+		Ins | 7,
+		Ins | 8,
+		Ins | 11,
+		Ins | 14,
+		Ins | 15,
+
+		Ins | 4,
+	})
+
+	f.Fuzz(func(t *testing.T, dat []uint8) {
+		tree := &Tree[uint8, uint8]{
+			KeyFn: func(x uint8) uint8 { return x },
+		}
+		checkTree(t, tree)
+		for _, b := range dat {
+			ins := (b & 0b0100_0000) != 0
+			val := (b & 0b0011_1111)
+			if ins {
+				t.Logf("Insert(%v)", val)
+				tree.Insert(val)
+				node := tree.Lookup(val)
+				require.NotNil(t, node)
+				assert.Equal(t, val, node.Value)
+			} else {
+				t.Logf("Delete(%v)", val)
+				tree.Delete(val)
+				assert.Nil(t, tree.Lookup(val))
+			}
+			checkTree(t, tree)
+		}
+	})
+}