(转)伸展树 ( Splay tree )

MiYu原创, 转帖请注明 : 转载自 ______________白白の屋 代码tree_node * splay (int i, tree_node * t) {
tree_node N, *l, *r, *y;
if (t == NULL)
return t;
N.left = N.right = NULL;
l = r = &N;

for (;;)
{
if (i < t->item)
{
if (t->left == NULL)
break;
if (i < t->left->item)
{
y = t->left; /* rotate right */
t->left = y->right;
y->right = t;
t = y;
if (t->left == NULL)
break;
}
r->left = t; /* link right */
r = t;
t = t->left;
} else if (i > t->item)
{
if (t->right == NULL)
break;
if (i > t->right->item)
{
y = t->right; /* rotate left */
t->right = y->left;
y->left = t;
t = y;
if (t->right == NULL)
break;
}
l->right = t; /* link left */
l = t;
t = t->right;
} else {
break;
}
}
l->right = t->left; /* assemble */
r->left = t->right;
t->left = N.right;
t->right = N.left;
return t;
}
Rotate right(查找10)：

代码 /*
**将i插入树t中,返回树的根结点(item值==i)
*/
tree_node* ST_insert(int i, tree_node *t) {
/* Insert i into the tree t, unless it's already there. */
/* Return a pointer to the resulting tree. */
tree_node* node;

node = (tree_node *) malloc (sizeof (tree_node));
if (node == NULL){
printf("Ran out of space\n");
exit(1);
}
node->item = i;
if (t == NULL) {
node->left = node->right = NULL;
size = 1;
return node;
}
t = splay(i,t);
if (i < t->item) { //令t为i的右子树
node->left = t->left;
node->right = t;
t->left = NULL;
size ++;
return node;
} else if (i > t->item) { //令t为i的左子树
node->right = t->right;
node->left = t;
t->right = NULL;
size++;
return node;
} else {
free(node); //i值已经存在于树t中
return t;
}
}3.3、删除操作

代码 /*
**从树中删除i,返回树的根结点
*/
tree_node* ST_delete(int i, tree_node* t) {
/* Deletes i from the tree if it's there. */
/* Return a pointer to the resulting tree. */
tree_node* x;
if (t==NULL)
return NULL;
t = splay(i,t);
if (i == t->item) { /* found it */
if (t->left == NULL) { //左子树为空,则x指向右子树即可
x = t->right;
} else {
x = splay(i, t->left); //查找左子树中最大结点max,令右子树为max的右子树
x->right = t->right;
}
size--;
free(t);
return x;
}
return t; /* It wasn't there */
}完整代码：

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

int size; //结点数量

#define NUM 20

typedef struct tree_node{
struct tree_node* left;
struct tree_node* right;
int item;
}tree_node;

tree_node* splay (int i, tree_node* t) {
tree_node N, *l, *r, *y;

if (t == NULL)
return t;

N.left = N.right = NULL;
l = r = &N;

for (;;)
{
if (i < t->item)
{
if (t->left == NULL)
break;
if (i < t->left->item)
{
y = t->left; /* rotate right */
t->left = y->right;
y->right = t;
t = y;
if (t->left == NULL)
break;
}
r->left = t; /* link right */
r = t;
t = t->left;
} else if (i > t->item)
{
if (t->right == NULL)
break;
if (i > t->right->item)
{
y = t->right; /* rotate left */
t->right = y->left;
y->left = t;
t = y;
if (t->right == NULL)
break;
}
l->right = t; /* link left */
l = t;
t = t->right;
} else {
break;
}
}
l->right = t->left; /* assemble */
r->left = t->right;
t->left = N.right;
t->right = N.left;
return t;
}

/*
**将i插入树t中,返回树的根结点(item值==i)
*/
tree_node* ST_insert(int i, tree_node *t) {
/* Insert i into the tree t, unless it's already there. */
/* Return a pointer to the resulting tree. */
tree_node* node;

node = (tree_node *) malloc (sizeof (tree_node));
if (node == NULL){
printf("Ran out of space\n");
exit(1);
}
node->item = i;
if (t == NULL) {
node->left = node->right = NULL;
size = 1;
return node;
}
t = splay(i,t);
if (i < t->item) { //令t为i的右子树
node->left = t->left;
node->right = t;
t->left = NULL;
size ++;
return node;
} else if (i > t->item) { //令t为i的左子树
node->right = t->right;
node->left = t;
t->right = NULL;
size++;
return node;
} else {
free(node); //i值已经存在于树t中
return t;
}
}

/*
**从树中删除i,返回树的根结点
*/
tree_node* ST_delete(int i, tree_node* t) {
/* Deletes i from the tree if it's there. */
/* Return a pointer to the resulting tree. */
tree_node* x;
if (t==NULL)
return NULL;
t = splay(i,t);
if (i == t->item) { /* found it */
if (t->left == NULL) { //左子树为空,则x指向右子树即可
x = t->right;
} else {
x = splay(i, t->left); //查找左子树中最大结点max,令右子树为max的右子树
x->right = t->right;
}
size--;
free(t);
return x;
}
return t; /* It wasn't there */
}

void ST_inoder_traverse(tree_node* node)
{
if(node != NULL)
{
ST_inoder_traverse(node->left);
printf("%d ", node->item);
ST_inoder_traverse(node->right);
}
}

void ST_pre_traverse(tree_node* node)
{
if(node != NULL)
{
printf("%d ", node->item);
ST_pre_traverse(node->left);
ST_pre_traverse(node->right);
}
}

void main() {
/* A sample use of these functions. Start with the empty tree, */
/* insert some stuff into it, and then delete it */
tree_node* root;
int i;

root = NULL; /* the empty tree */
size = 0;

for(i = 0; i < NUM; i++)
root = ST_insert(rand()%NUM, root);

ST_pre_traverse(root);
printf("\n");
ST_inoder_traverse(root);

for(i = 0; i < NUM; i++)
root = ST_delete(i, root);

printf("\nsize = %d\n", size);
}