c++实现b树

B树是一种多路搜索树，常用于数据库和文件系统等场景中。以下是一个简单的C++实现B树的示例：

#include <iostream>
#include <vector>

// B树节点
template<typename T>
class BTreeNode {
public:
    bool leaf; // 是否为叶子节点
    std::vector<T> keys; // 键值列表
    std::vector<BTreeNode<T>*> children; // 子节点列表

    // 构造函数
    BTreeNode(bool _leaf) : leaf(_leaf) {}

    // 在节点中查找键值
    int findKey(const T& key) {
        int idx = 0;
        while (idx < keys.size() && keys[idx] < key) ++idx;
        return idx;
    }

    // 插入键值
    void insertNonFull(const T& key) {
        int idx = keys.size() - 1;
        if (leaf) {
            while (idx >= 0 && keys[idx] > key) {
                keys[idx + 1] = keys[idx];
                --idx;
            }
            keys[idx + 1] = key;
        } else {
            while (idx >= 0 && keys[idx] > key) --idx;
            if (children[idx + 1]->keys.size() == 2 * t - 1) {
                splitChild(idx + 1, children[idx + 1]);
                if (keys[idx + 1] < key) ++idx;
            }
            children[idx + 1]->insertNonFull(key);
        }
    }

    // 分裂子节点
    void splitChild(int i, BTreeNode<T>* y) {
        BTreeNode<T>* z = new BTreeNode<T>(y->leaf);
        z->keys.resize(t - 1);
        if (!y->leaf) {
            z->children.resize(t);
        }
        for (int j = 0; j < t - 1; ++j) {
            z->keys[j] = y->keys[j + t];
        }
        if (!y->leaf) {
            for (int j = 0; j < t; ++j) {
                z->children[j] = y->children[j + t];
            }
        }
        y->keys.resize(t - 1);
        if (!y->leaf) {
            y->children.resize(t);
        }
        for (int j = keys.size(); j >= i + 1; --j) {
            children[j + 1] = children[j];
        }
        children[i + 1] = z;
        for (int j = keys.size() - 1; j >= i; --j) {
            keys[j + 1] = keys[j];
        }
        keys[i] = y->keys[t - 1];
    }

private:
    static constexpr int t = 3; // B树的度数
};

// B树
template<typename T>
class BTree {
public:
    BTree() : root(nullptr) {}

    // 查找键值
    bool search(const T& key) {
        return root ? root->search(key) : false;
    }

    // 插入键值
    void insert(const T& key) {
        if (!root) {
            root = new BTreeNode<T>(true);
            root->keys.push_back(key);
        } else {
            if (root->keys.size() == 2 * BTreeNode<T>::t - 1) {
                BTreeNode<T>* s = new BTreeNode<T>(false);
                s->children.push_back(root);
                s->splitChild(0, root);
                int i = 0;
                if (s->keys[0] < key) ++i;
                s->children[i]->insertNonFull(key);
                root = s;
            } else {
                root->insertNonFull(key);
            }
        }
    }

private:
    BTreeNode<T>* root;
};

int main() {
    BTree<int> tree;
    tree.insert(10);
    tree.insert(20);
    tree.insert(5);
    tree.insert(6);
    tree.insert(12);
    tree.insert(30);

    std::cout << "Search for 6: " << (tree.search(6) ? "Found" : "Not found") << std::endl;
    std::cout << "Search for 7: " << (tree.search(7) ? "Found" : "Not found") << std::endl;

    return 0;
}

这是一个简单的B树实现，包含了查找和插入操作。在实际应用中，可能需要更多的功能和优化。