Splay Tree的删除操作

Splay Tree的插入操作，搜索操作，和删除操作都实现了，那么就可以使用来解题了。

指针的删除操作的处理还是那么难的，很多坎需要避开.

同一个坎还是坑了我好多次，就是指针传递的问题，什么时候需要修改指针本身的值，就必须返回指针或者传递指针的指针，或者传递指针的的实参。

这里的删除操作就是需要改变传递到函数的指针本身的，所以我这里使用了返回指针操作。

还有删除树的问题，之前的代码没做删除操作，所以没问题，现在需要逐个节点删除，所以要小心不能把整个树都删除了。

至此， splay 树的功能差不多完善了。

代码中注释标明了几个坑都被我碰到了。

#pragma once#include <stdio.h>class SplayTreeComplete{struct Node{int key;Node *left, *right;explicit Node(int k):key(k),left(NULL),right(NULL){}/*~Node(){教训：这样的话整颗树都删除了，不能这么删除，要逐个节点删除if (left) delete left, left = NULL;if (right) delete right, right = NULL;}*/};Node *leftRotate(Node *x){Node *y = x->right;x->right = y->left;y->left = x;return y;}Node *rightRotate(Node *x){Node *y = x->left;x->left = y->right;y->right = x;return y;}Node *splay(Node *root, const int key){if (!root || key == root->key) return root;if (key < root->key){if (!root->left) return root;if (key < root->left->key){root->left->left = splay(root->left->left, key);root = rightRotate(root);}else if (root->left->key < key){root->left->right = splay(root->left->right, key);if (root->left->right) root->left = leftRotate(root->left);}return root->left? rightRotate(root) : root;}if (!root->right) return root;if (root->right->key < key){root->right->right = splay(root->right->right, key);root = leftRotate(root);}else if (key < root->right->key){root->right->left = splay(root->right->left, key);if (root->right->left) root->right = rightRotate(root->right);}return root->right? leftRotate(root) : root;}Node *insert(Node *root, const int key){if (!root) return new Node((int)key);//别忘了创建新的节点root = splay(root, key);//别忘了 root = if (key == root->key) return root;Node *newNode = new Node((int)key);if (key < root->key){newNode->right = root;newNode->left = root->left;root->left = NULL;//别漏了这句，否则破坏了树结构}else{newNode->left = root;newNode->right = root->right;root->right = NULL;}return newNode;}Node *deleteNode(Node *root, const int key){if (!root) return root;root = splay(root, key);if (key == root->key){if (!root->left){Node *x = root;root = root->right;delete x, x = NULL;}else{Node *x = root->right;Node *y = root->left;delete root;root = splay(y, key);root->right = x;}}return root;}void preOrder(Node *root){if (root != NULL){printf("%d ", root->key);preOrder(root->left);preOrder(root->right);}}public:SplayTreeComplete(){Node *root = NULL;int keys[] = {100, 50, 200, 40, 30, 20, 25};int n = sizeof(keys) / sizeof(keys[0]);for (int i = 0; i < n; i++){root = insert(root, keys[i]);}printf("\nInser create Preorder traversal Splay tree is \n");preOrder(root);putchar('\n');root = splay(root, 50);bool found = root->key == 50;printf("\n50 is %s the tree\n", found? "in" : "not in");root = deleteNode(root, 50);//root 发生改变了，所以必须返回新的指针值root = splay(root, 50);found = root->key == 50;printf("\n50 is %s the tree\n", found? "in" : "not in");printf("\nInser create Preorder traversal Splay tree is \n");preOrder(root);putchar('\n');deleteTree(root);}void deleteTree(Node *root){if (root){deleteTree(root->left);deleteTree(root->right);delete root, root = NULL;}}};