B树的插入

向B树中插入一个元素包括两个事件：**搜索要插入元素的合适节点**以及**在需要时分裂节点**。插入操作总是自底向上进行的。

下面我们来理解这两个事件。

插入操作

如果树为空，则分配一个根节点并插入键。
更新节点中允许的键数。
搜索要插入的合适节点。
如果节点已满，请按照以下步骤操作。
按递增顺序插入元素。
现在，元素数量超过了其限制。因此，在中间值处分裂。
将中间键向上推，并将左侧的键作为左子节点，右侧的键作为右子节点。
如果节点未满，请按照以下步骤操作。
按递增顺序插入节点。

插入示例

下面我们通过图示来理解插入操作。

要插入的元素是 8, 9, 10, 11, 15, 20, 17。

Inserting elements into a B-tree — 将元素插入B树

插入元素的算法

BreeInsertion(T, k)
r  root[T]
if n[r] = 2t - 1
    s = AllocateNode()
    root[T] = s
    leaf[s] = FALSE
    n[s] <- 0
    c1[s] <- r
    BtreeSplitChild(s, 1, r)
    BtreeInsertNonFull(s, k)
else BtreeInsertNonFull(r, k)
BtreeInsertNonFull(x, k)
i = n[x]
if leaf[x]
    while i ≥ 1 and k < keyi[x]
        keyi+1 [x] = keyi[x]
        i = i - 1
    keyi+1[x] = k
    n[x] = n[x] + 1
else while i ≥ 1 and k < keyi[x]
        i = i - 1
    i = i + 1
    if n[ci[x]] == 2t - 1
        BtreeSplitChild(x, i, ci[x])
        if k &rt; keyi[x]
            i = i + 1
    BtreeInsertNonFull(ci[x], k)
BtreeSplitChild(x, i)
BtreeSplitChild(x, i, y)
z = AllocateNode()
leaf[z] = leaf[y]
n[z] = t - 1
for j = 1 to t - 1
    keyj[z] = keyj+t[y]
if not leaf [y]
    for j = 1 to t
        cj[z] = cj + t[y]
n[y] = t - 1
for j = n[x] + 1 to i + 1
    cj+1[x] = cj[x]
ci+1[x] = z
for j = n[x] to i
    keyj+1[x] = keyj[x]
keyi[x] = keyt[y]
n[x] = n[x] + 1

Python、Java 和 C/C++ 示例

Python

Java

C++

# Inserting a key on a B-tree in Python


# Create a node
class BTreeNode:
    def __init__(self, leaf=False):
        self.leaf = leaf
        self.keys = []
        self.child = []


# Tree
class BTree:
    def __init__(self, t):
        self.root = BTreeNode(True)
        self.t = t

    # Insert node
    def insert(self, k):
        root = self.root
        if len(root.keys) == (2 * self.t) - 1:
            temp = BTreeNode()
            self.root = temp
            temp.child.insert(0, root)
            self.split_child(temp, 0)
            self.insert_non_full(temp, k)
        else:
            self.insert_non_full(root, k)

    # Insert nonfull
    def insert_non_full(self, x, k):
        i = len(x.keys) - 1
        if x.leaf:
            x.keys.append((None, None))
            while i >= 0 and k[0] < x.keys[i][0]:
                x.keys[i + 1] = x.keys[i]
                i -= 1
            x.keys[i + 1] = k
        else:
            while i >= 0 and k[0] < x.keys[i][0]:
                i -= 1
            i += 1
            if len(x.child[i].keys) == (2 * self.t) - 1:
                self.split_child(x, i)
                if k[0] > x.keys[i][0]:
                    i += 1
            self.insert_non_full(x.child[i], k)

    # Split the child
    def split_child(self, x, i):
        t = self.t
        y = x.child[i]
        z = BTreeNode(y.leaf)
        x.child.insert(i + 1, z)
        x.keys.insert(i, y.keys[t - 1])
        z.keys = y.keys[t: (2 * t) - 1]
        y.keys = y.keys[0: t - 1]
        if not y.leaf:
            z.child = y.child[t: 2 * t]
            y.child = y.child[0: t - 1]

    # Print the tree
    def print_tree(self, x, l=0):
        print("Level ", l, " ", len(x.keys), end=":")
        for i in x.keys:
            print(i, end=" ")
        print()
        l += 1
        if len(x.child) > 0:
            for i in x.child:
                self.print_tree(i, l)


def main():
    B = BTree(3)

    for i in range(10):
        B.insert((i, 2 * i))

    B.print_tree(B.root)


if __name__ == '__main__':
    main()

// Inserting a key on a B-tree in Java 

public class BTree {

  private int T;

  // Node Creation
  public class Node {
    int n;
    int key[] = new int[2 * T - 1];
    Node child[] = new Node[2 * T];
    boolean leaf = true;

    public int Find(int k) {
      for (int i = 0; i < this.n; i++) {
        if (this.key[i] == k) {
          return i;
        }
      }
      return -1;
    };
  }

  public BTree(int t) {
    T = t;
    root = new Node();
    root.n = 0;
    root.leaf = true;
  }

  private Node root;

  // split
  private void split(Node x, int pos, Node y) {
    Node z = new Node();
    z.leaf = y.leaf;
    z.n = T - 1;
    for (int j = 0; j < T - 1; j++) {
      z.key[j] = y.key[j + T];
    }
    if (!y.leaf) {
      for (int j = 0; j < T; j++) {
        z.child[j] = y.child[j + T];
      }
    }
    y.n = T - 1;
    for (int j = x.n; j >= pos + 1; j--) {
      x.child[j + 1] = x.child[j];
    }
    x.child[pos + 1] = z;

    for (int j = x.n - 1; j >= pos; j--) {
      x.key[j + 1] = x.key[j];
    }
    x.key[pos] = y.key[T - 1];
    x.n = x.n + 1;
  }

  // insert key
  public void insert(final int key) {
    Node r = root;
    if (r.n == 2 * T - 1) {
      Node s = new Node();
      root = s;
      s.leaf = false;
      s.n = 0;
      s.child[0] = r;
      split(s, 0, r);
      _insert(s, key);
    } else {
      _insert(r, key);
    }
  }

  // insert node
  final private void _insert(Node x, int k) {

    if (x.leaf) {
      int i = 0;
      for (i = x.n - 1; i >= 0 && k < x.key[i]; i--) {
        x.key[i + 1] = x.key[i];
      }
      x.key[i + 1] = k;
      x.n = x.n + 1;
    } else {
      int i = 0;
      for (i = x.n - 1; i >= 0 && k < x.key[i]; i--) {
      }
      ;
      i++;
      Node tmp = x.child[i];
      if (tmp.n == 2 * T - 1) {
        split(x, i, tmp);
        if (k > x.key[i]) {
          i++;
        }
      }
      _insert(x.child[i], k);
    }

  }

  public void display() {
    display(root);
  }

  // Display the tree
  private void display(Node x) {
    assert (x == null);
    for (int i = 0; i < x.n; i++) {
      System.out.print(x.key[i] + " ");
    }
    if (!x.leaf) {
      for (int i = 0; i < x.n + 1; i++) {
        display(x.child[i]);
      }
    }
  }

  public static void main(String[] args) {
    BTree b = new BTree(3);
    b.insert(8);
    b.insert(9);
    b.insert(10);
    b.insert(11);
    b.insert(15);
    b.insert(20);
    b.insert(17);

    b.display();
  }
}

// insertioning a key on a B-tree in C

#include <stdio.h>
#include <stdlib.h>

#define MAX 3
#define MIN 2

struct btreeNode {
  int item[MAX + 1], count;
  struct btreeNode *link[MAX + 1];
};

struct btreeNode *root;

// Node creation
struct btreeNode *createNode(int item, struct btreeNode *child) {
  struct btreeNode *newNode;
  newNode = (struct btreeNode *)malloc(sizeof(struct btreeNode));
  newNode->item[1] = item;
  newNode->count = 1;
  newNode->link[0] = root;
  newNode->link[1] = child;
  return newNode;
}

// Insert
void insertValue(int item, int pos, struct btreeNode *node,
          struct btreeNode *child) {
  int j = node->count;
  while (j > pos) {
    node->item[j + 1] = node->item[j];
    node->link[j + 1] = node->link[j];
    j--;
  }
  node->item[j + 1] = item;
  node->link[j + 1] = child;
  node->count++;
}

// Split node
void splitNode(int item, int *pval, int pos, struct btreeNode *node,
         struct btreeNode *child, struct btreeNode **newNode) {
  int median, j;

  if (pos > MIN)
    median = MIN + 1;
  else
    median = MIN;

  *newNode = (struct btreeNode *)malloc(sizeof(struct btreeNode));
  j = median + 1;
  while (j <= MAX) {
    (*newNode)->item[j - median] = node->item[j];
    (*newNode)->link[j - median] = node->link[j];
    j++;
  }
  node->count = median;
  (*newNode)->count = MAX - median;

  if (pos <= MIN) {
    insertValue(item, pos, node, child);
  } else {
    insertValue(item, pos - median, *newNode, child);
  }
  *pval = node->item[node->count];
  (*newNode)->link[0] = node->link[node->count];
  node->count--;
}

// Set the value of node
int setNodeValue(int item, int *pval,
           struct btreeNode *node, struct btreeNode **child) {
  int pos;
  if (!node) {
    *pval = item;
    *child = NULL;
    return 1;
  }

  if (item < node->item[1]) {
    pos = 0;
  } else {
    for (pos = node->count;
       (item < node->item[pos] && pos > 1); pos--)
      ;
    if (item == node->item[pos]) {
      printf("Duplicates not allowed\n");
      return 0;
    }
  }
  if (setNodeValue(item, pval, node->link[pos], child)) {
    if (node->count < MAX) {
      insertValue(*pval, pos, node, *child);
    } else {
      splitNode(*pval, pval, pos, node, *child, child);
      return 1;
    }
  }
  return 0;
}

// Insert the value
void insertion(int item) {
  int flag, i;
  struct btreeNode *child;

  flag = setNodeValue(item, &i, root, &child);
  if (flag)
    root = createNode(i, child);
}

// Copy the successor
void copySuccessor(struct btreeNode *myNode, int pos) {
  struct btreeNode *dummy;
  dummy = myNode->link[pos];

  for (; dummy->link[0] != NULL;)
    dummy = dummy->link[0];
  myNode->item[pos] = dummy->item[1];
}

// Do rightshift
void rightShift(struct btreeNode *myNode, int pos) {
  struct btreeNode *x = myNode->link[pos];
  int j = x->count;

  while (j > 0) {
    x->item[j + 1] = x->item[j];
    x->link[j + 1] = x->link[j];
  }
  x->item[1] = myNode->item[pos];
  x->link[1] = x->link[0];
  x->count++;

  x = myNode->link[pos - 1];
  myNode->item[pos] = x->item[x->count];
  myNode->link[pos] = x->link[x->count];
  x->count--;
  return;
}

// Do leftshift
void leftShift(struct btreeNode *myNode, int pos) {
  int j = 1;
  struct btreeNode *x = myNode->link[pos - 1];

  x->count++;
  x->item[x->count] = myNode->item[pos];
  x->link[x->count] = myNode->link[pos]->link[0];

  x = myNode->link[pos];
  myNode->item[pos] = x->item[1];
  x->link[0] = x->link[1];
  x->count--;

  while (j <= x->count) {
    x->item[j] = x->item[j + 1];
    x->link[j] = x->link[j + 1];
    j++;
  }
  return;
}

// Merge the nodes
void mergeNodes(struct btreeNode *myNode, int pos) {
  int j = 1;
  struct btreeNode *x1 = myNode->link[pos], *x2 = myNode->link[pos - 1];

  x2->count++;
  x2->item[x2->count] = myNode->item[pos];
  x2->link[x2->count] = myNode->link[0];

  while (j <= x1->count) {
    x2->count++;
    x2->item[x2->count] = x1->item[j];
    x2->link[x2->count] = x1->link[j];
    j++;
  }

  j = pos;
  while (j < myNode->count) {
    myNode->item[j] = myNode->item[j + 1];
    myNode->link[j] = myNode->link[j + 1];
    j++;
  }
  myNode->count--;
  free(x1);
}

// Adjust the node
void adjustNode(struct btreeNode *myNode, int pos) {
  if (!pos) {
    if (myNode->link[1]->count > MIN) {
      leftShift(myNode, 1);
    } else {
      mergeNodes(myNode, 1);
    }
  } else {
    if (myNode->count != pos) {
      if (myNode->link[pos - 1]->count > MIN) {
        rightShift(myNode, pos);
      } else {
        if (myNode->link[pos + 1]->count > MIN) {
          leftShift(myNode, pos + 1);
        } else {
          mergeNodes(myNode, pos);
        }
      }
    } else {
      if (myNode->link[pos - 1]->count > MIN)
        rightShift(myNode, pos);
      else
        mergeNodes(myNode, pos);
    }
  }
}

// Traverse the tree
void traversal(struct btreeNode *myNode) {
  int i;
  if (myNode) {
    for (i = 0; i < myNode->count; i++) {
      traversal(myNode->link[i]);
      printf("%d ", myNode->item[i + 1]);
    }
    traversal(myNode->link[i]);
  }
}

int main() {
  int item, ch;

  insertion(8);
  insertion(9);
  insertion(10);
  insertion(11);
  insertion(15);
  insertion(16);
  insertion(17);
  insertion(18);
  insertion(20);
  insertion(23);

  traversal(root);
}

// Inserting a key on a B-tree in C++

#include <iostream>
using namespace std;

class Node {
  int *keys;
  int t;
  Node **C;
  int n;
  bool leaf;

   public:
  Node(int _t, bool _leaf);

  void insertNonFull(int k);
  void splitChild(int i, Node *y);
  void traverse();

  friend class BTree;
};

class BTree {
  Node *root;
  int t;

   public:
  BTree(int _t) {
    root = NULL;
    t = _t;
  }

  void traverse() {
    if (root != NULL)
      root->traverse();
  }

  void insert(int k);
};

Node::Node(int t1, bool leaf1) {
  t = t1;
  leaf = leaf1;

  keys = new int[2 * t - 1];
  C = new Node *[2 * t];

  n = 0;
}

// Traverse the nodes
void Node::traverse() {
  int i;
  for (i = 0; i < n; i++) {
    if (leaf == false)
      C[i]->traverse();
    cout << " " << keys[i];
  }

  if (leaf == false)
    C[i]->traverse();
}

// Insert the node
void BTree::insert(int k) {
  if (root == NULL) {
    root = new Node(t, true);
    root->keys[0] = k;
    root->n = 1;
  } else {
    if (root->n == 2 * t - 1) {
      Node *s = new Node(t, false);

      s->C[0] = root;

      s->splitChild(0, root);

      int i = 0;
      if (s->keys[0] < k)
        i++;
      s->C[i]->insertNonFull(k);

      root = s;
    } else
      root->insertNonFull(k);
  }
}

// Insert non full condition
void Node::insertNonFull(int k) {
  int i = n - 1;

  if (leaf == true) {
    while (i >= 0 && keys[i] > k) {
      keys[i + 1] = keys[i];
      i--;
    }

    keys[i + 1] = k;
    n = n + 1;
  } else {
    while (i >= 0 && keys[i] > k)
      i--;

    if (C[i + 1]->n == 2 * t - 1) {
      splitChild(i + 1, C[i + 1]);

      if (keys[i + 1] < k)
        i++;
    }
    C[i + 1]->insertNonFull(k);
  }
}

// split the child
void Node::splitChild(int i, Node *y) {
  Node *z = new Node(y->t, y->leaf);
  z->n = t - 1;

  for (int j = 0; j < t - 1; j++)
    z->keys[j] = y->keys[j + t];

  if (y->leaf == false) {
    for (int j = 0; j < t; j++)
      z->C[j] = y->C[j + t];
  }

  y->n = t - 1;
  for (int j = n; j >= i + 1; j--)
    C[j + 1] = C[j];

  C[i + 1] = z;

  for (int j = n - 1; j >= i; j--)
    keys[j + 1] = keys[j];

  keys[i] = y->keys[t - 1];
  n = n + 1;
}

int main() {
  BTree t(3);
  t.insert(8);
  t.insert(9);
  t.insert(10);
  t.insert(11);
  t.insert(15);
  t.insert(16);
  t.insert(17);
  t.insert(18);
  t.insert(20);
  t.insert(23);

  cout << "The B-tree is: ";
  t.traverse();
}

热门教程

热门实例

参考资料

认证课程

成为一名认证的 Python
程序员。

热门教程

参考资料

热门实例

DSA 简介

数据结构 (I)

数据结构 (II)

基于树的 DSA (I)

基于树的 DSA (II)

基于图的 DSA

排序和搜索算法

贪婪算法

动态规划

其他算法

B树的插入

插入操作

插入示例

插入元素的算法

Python、Java 和 C/C++ 示例

目录

热门教程

热门实例

参考资料

认证课程

成为一名认证的 Python程序员。

热门教程

参考资料

热门实例

DSA 简介

数据结构 (I)

数据结构 (II)

基于树的 DSA (I)

基于树的 DSA (II)

基于图的 DSA

排序和搜索算法

贪婪算法

动态规划

其他算法

DSA 教程

B树的插入

插入操作

插入示例

插入元素的算法

Python、Java 和 C/C++ 示例

目录

相关教程

成为一名认证的 Python
程序员。