leetcode/avl/avl_test.go

package avl

import (
	"reflect"
	"testing"
)

func TestAVLBasicOperations(t *testing.T) {
	tree := NewAVLTree[int]()

	if tree.Height() != 0 {
		t.Fatalf("空树 Height() = %d, want 0", tree.Height())
	}
	if _, ok := tree.Min(); ok {
		t.Fatal("空树 Min() 的 ok = true, want false")
	}
	if _, ok := tree.Max(); ok {
		t.Fatal("空树 Max() 的 ok = true, want false")
	}
	if tree.Search(1) {
		t.Fatal("空树 Search(1) = true, want false")
	}

	for _, v := range []int{6, 3, 2, 1, 4, 5} {
		tree.Insert(v)
	}

	if got, want := tree.Inorder(), []int{1, 2, 3, 4, 5, 6}; !reflect.DeepEqual(got, want) {
		t.Fatalf("Inorder() = %v, want %v", got, want)
	}
	if !tree.Search(1) || !tree.Search(6) || tree.Search(7) {
		t.Fatalf("Search 结果不正确：Search(1)=%v, Search(6)=%v, Search(7)=%v", tree.Search(1), tree.Search(6), tree.Search(7))
	}
	if got, ok := tree.Min(); !ok || got != 1 {
		t.Fatalf("Min() = (%d, %v), want (1, true)", got, ok)
	}
	if got, ok := tree.Max(); !ok || got != 6 {
		t.Fatalf("Max() = (%d, %v), want (6, true)", got, ok)
	}
	assertAVL(t, tree.Root, nil, nil)
}

func TestAVLDelete(t *testing.T) {
	cases := []struct {
		name    string
		values  []int
		delete  int
		want    []int
		wantMin *int
		wantMax *int
	}{
		{
			name:   "delete only root leaf",
			values: []int{10},
			delete: 10,
			want:   []int{},
		},
		{
			name:    "delete root with one child",
			values:  []int{10, 5},
			delete:  10,
			want:    []int{5},
			wantMin: intPtr(5),
			wantMax: intPtr(5),
		},
		{
			name:    "delete non-root leaf and update parent height",
			values:  []int{10, 5, 15},
			delete:  5,
			want:    []int{10, 15},
			wantMin: intPtr(10),
			wantMax: intPtr(15),
		},
		{
			name:    "delete non-root with one child",
			values:  []int{10, 5, 15, 12},
			delete:  15,
			want:    []int{5, 10, 12},
			wantMin: intPtr(5),
			wantMax: intPtr(12),
		},
		{
			name:    "delete root with two children successor is leaf",
			values:  []int{10, 5, 15, 12, 18},
			delete:  10,
			want:    []int{5, 12, 15, 18},
			wantMin: intPtr(5),
			wantMax: intPtr(18),
		},
		{
			name:    "delete root with two children successor has right child",
			values:  []int{10, 5, 20, 15, 25, 17},
			delete:  10,
			want:    []int{5, 15, 17, 20, 25},
			wantMin: intPtr(5),
			wantMax: intPtr(25),
		},
		{
			name:    "delete missing value leaves tree unchanged",
			values:  []int{10, 5, 20, 15, 25},
			delete:  99,
			want:    []int{5, 10, 15, 20, 25},
			wantMin: intPtr(5),
			wantMax: intPtr(25),
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			tree := NewAVLTree[int]()
			for _, v := range tc.values {
				tree.Insert(v)
			}

			tree.Delete(tc.delete)

			if got := tree.Inorder(); !reflect.DeepEqual(got, tc.want) {
				t.Fatalf("Delete(%d) 后 Inorder() = %v, want %v", tc.delete, got, tc.want)
			}
			if tree.Search(tc.delete) && tc.delete != 99 {
				t.Fatalf("Delete(%d) 后 Search(%d) = true, want false", tc.delete, tc.delete)
			}
			if tc.wantMin == nil {
				if tree.Height() != 0 {
					t.Fatalf("删空树后 Height() = %d, want 0", tree.Height())
				}
				if _, ok := tree.Min(); ok {
					t.Fatal("删空树后 Min() 的 ok = true, want false")
				}
				if _, ok := tree.Max(); ok {
					t.Fatal("删空树后 Max() 的 ok = true, want false")
				}
			} else {
				if got, ok := tree.Min(); !ok || got != *tc.wantMin {
					t.Fatalf("Min() = (%d, %v), want (%d, true)", got, ok, *tc.wantMin)
				}
				if got, ok := tree.Max(); !ok || got != *tc.wantMax {
					t.Fatalf("Max() = (%d, %v), want (%d, true)", got, ok, *tc.wantMax)
				}
			}
			assertAVL(t, tree.Root, nil, nil)
		})
	}
}

func TestAVLDeleteRebalancesOnPathToRoot(t *testing.T) {
	tree := NewAVLTree[int]()
	for _, v := range []int{4, 2, 6, 1, 3, 5, 7} {
		tree.Insert(v)
	}

	for _, v := range []int{7, 6, 5} {
		tree.Delete(v)
		assertAVL(t, tree.Root, nil, nil)
	}

	if got, want := tree.Inorder(), []int{1, 2, 3, 4}; !reflect.DeepEqual(got, want) {
		t.Fatalf("连续删除后 Inorder() = %v, want %v", got, want)
	}
}

func assertAVL(t *testing.T, node *AVLNode[int], lower, upper *int) int {
	t.Helper()
	if node == nil {
		return 0
	}
	if lower != nil && node.Val <= *lower {
		t.Fatalf("BST 性质被破坏：节点 %d <= 下界 %d", node.Val, *lower)
	}
	if upper != nil && node.Val >= *upper {
		t.Fatalf("BST 性质被破坏：节点 %d >= 上界 %d", node.Val, *upper)
	}

	leftHeight := assertAVL(t, node.Left, lower, &node.Val)
	rightHeight := assertAVL(t, node.Right, &node.Val, upper)
	if balanceFactor := leftHeight - rightHeight; balanceFactor < -1 || balanceFactor > 1 {
		t.Fatalf("节点 %d 的 BF = %d, want [-1, 1]", node.Val, balanceFactor)
	}

	wantHeight := max(leftHeight, rightHeight) + 1
	if node.Height != wantHeight {
		t.Fatalf("节点 %d 的 Height = %d, want %d", node.Val, node.Height, wantHeight)
	}
	return wantHeight
}

func intPtr(v int) *int {
	return &v
}