Woolsey渣渣要好好學習
B+樹是一種n叉樹，它將所有資料存在一個level中。B+ 樹的特點是能夠保持資料穩定有序，其插入與修改擁有較穩定的對數時間複雜度。因此B+樹被應用於資料庫和作業系統的檔案系統中。
B+樹的理解沒有紅黑樹這麼複雜，本文將首先簡要介紹B+樹，然後分析B+樹的先關題目。本文重點是最後一部分。
介紹
A B+ tree of order M is a tree with the following structural properties:
(1) The root is either a leaf or has between 2 and M children.
(2) All nonleaf nodes (except the root) have between
(3) All leaves are at the same depth.
Assume each nonroot leaf also has between
需要注意：
- 每個儲存資料的葉節點，其中的資料數量在
⌈M/2⌉ 與 M之間（閉區間）。若超出這個區間，則進行調整。 - 從空樹開始時，資料首先存放在根節點中，當根節點的資料大於M時再進行調整。
- 根的子節點數最小為2， 而其他非根節點的子節點數最小為
⌈M/2⌉
相關題目
Insert 3, 1, 4, 5, 9, 2, 6, 8, 7, 0 into an initially empty 2-3 tree (with splitting). Which one of the following statements is FALSE? (2分)
A. 7 and 8 are in the same node
B. the parent of the node containing 5 has 3 children
C. the first key stored in the root is 6
D. there are 5 leaf nodes
故選A
After deleting 9 from the 2-3 tree given in the figure, which one of the following statements is FALSE? (2分)
A. the root is full
B. the second key stored in the root is 6
C. 6 and 8 are in the same node
D. 6 and 5 are in the same node
故選D
Which of the following statements concerning a B+ tree of order M is TRUE? (2分)
A. the root always has between 2 and M children
B. not all leaves are at the same depth
C. leaves and nonleaf nodes have some key values in common
D. all nonleaf nodes have between ⌈M/2⌉ and M children
A. 當只有root一個節點時，root沒有孩子。故錯。
B. 這違反了定義“所有葉節點位於同一深度”。
C. 正確。
D. 除了根節點外的非葉結點有 ⌈M/2⌉ 與 M 之間的子節點。
故選D