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red_black_tree.c
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red_black_tree.c
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#include "fileops_bankshot2.h"
#include "red_black_tree.h"
/***********************************************************************/
/* FUNCTION: RBTreeCreate */
/**/
/* INPUTS: All the inputs are names of functions. CompFunc takes to */
/* void pointers to keys and returns 1 if the first arguement is */
/* "greater than" the second. DestFunc takes a pointer to a key and */
/* destroys it in the appropriate manner when the node containing that */
/* key is deleted. InfoDestFunc is similiar to DestFunc except it */
/* recieves a pointer to the info of a node and destroys it. */
/* PrintFunc recieves a pointer to the key of a node and prints it. */
/* PrintInfo recieves a pointer to the info of a node and prints it. */
/* If RBTreePrint is never called the print functions don't have to be */
/* defined and NullFunction can be used. */
/**/
/* OUTPUT: This function returns a pointer to the newly created */
/* red-black tree. */
/**/
/* Modifies Input: none */
/***********************************************************************/
rb_red_blk_tree* RBTreeCreate( int (*CompFunc) (const void*,const void*),
void (*DestFunc) (void*),
void (*InfoDestFunc) (void*),
void (*PrintFunc) (const void*),
void (*PrintInfo)(void*)) {
rb_red_blk_tree* newTree;
rb_red_blk_node* temp;
newTree=(rb_red_blk_tree*)malloc(sizeof(rb_red_blk_tree));
newTree->Compare= CompFunc;
newTree->DestroyKey= DestFunc;
newTree->PrintKey= PrintFunc;
newTree->PrintInfo= PrintInfo;
newTree->DestroyInfo= InfoDestFunc;
/* see the comment in the rb_red_blk_tree structure in red_black_tree.h */
/* for information on nil and root */
temp=newTree->nil= (rb_red_blk_node*)malloc(sizeof(rb_red_blk_node));
temp->parent=temp->left=temp->right=temp;
temp->red=0;
temp->key=0;
temp=newTree->root= (rb_red_blk_node*)malloc(sizeof(rb_red_blk_node));
temp->parent=temp->left=temp->right=newTree->nil;
temp->key=0;
temp->red=0;
return(newTree);
}
/***********************************************************************/
/* FUNCTION: LeftRotate */
/**/
/* INPUTS: This takes a tree so that it can access the appropriate */
/* root and nil pointers, and the node to rotate on. */
/**/
/* OUTPUT: None */
/**/
/* Modifies Input: tree, x */
/**/
/* EFFECTS: Rotates as described in _Introduction_To_Algorithms by */
/* Cormen, Leiserson, Rivest (Chapter 14). Basically this */
/* makes the parent of x be to the left of x, x the parent of */
/* its parent before the rotation and fixes other pointers */
/* accordingly. */
/***********************************************************************/
void LeftRotate(rb_red_blk_tree* tree, rb_red_blk_node* x) {
rb_red_blk_node* y;
rb_red_blk_node* nil=tree->nil;
/* I originally wrote this function to use the sentinel for */
/* nil to avoid checking for nil. However this introduces a */
/* very subtle bug because sometimes this function modifies */
/* the parent pointer of nil. This can be a problem if a */
/* function which calls LeftRotate also uses the nil sentinel */
/* and expects the nil sentinel's parent pointer to be unchanged */
/* after calling this function. For example, when RBDeleteFixUP */
/* calls LeftRotate it expects the parent pointer of nil to be */
/* unchanged. */
y=x->right;
x->right=y->left;
if (y->left != nil) y->left->parent=x; /* used to use sentinel here */
/* and do an unconditional assignment instead of testing for nil */
y->parent=x->parent;
/* instead of checking if x->parent is the root as in the book, we */
/* count on the root sentinel to implicitly take care of this case */
if( x == x->parent->left) {
x->parent->left=y;
} else {
x->parent->right=y;
}
y->left=x;
x->parent=y;
#ifdef DEBUG_ASSERT
Assert(!tree->nil->red,"nil not red in LeftRotate");
#endif
}
/***********************************************************************/
/* FUNCTION: RighttRotate */
/**/
/* INPUTS: This takes a tree so that it can access the appropriate */
/* root and nil pointers, and the node to rotate on. */
/**/
/* OUTPUT: None */
/**/
/* Modifies Input?: tree, y */
/**/
/* EFFECTS: Rotates as described in _Introduction_To_Algorithms by */
/* Cormen, Leiserson, Rivest (Chapter 14). Basically this */
/* makes the parent of x be to the left of x, x the parent of */
/* its parent before the rotation and fixes other pointers */
/* accordingly. */
/***********************************************************************/
void RightRotate(rb_red_blk_tree* tree, rb_red_blk_node* y) {
rb_red_blk_node* x;
rb_red_blk_node* nil=tree->nil;
/* I originally wrote this function to use the sentinel for */
/* nil to avoid checking for nil. However this introduces a */
/* very subtle bug because sometimes this function modifies */
/* the parent pointer of nil. This can be a problem if a */
/* function which calls LeftRotate also uses the nil sentinel */
/* and expects the nil sentinel's parent pointer to be unchanged */
/* after calling this function. For example, when RBDeleteFixUP */
/* calls LeftRotate it expects the parent pointer of nil to be */
/* unchanged. */
x=y->left;
y->left=x->right;
if (nil != x->right) x->right->parent=y; /*used to use sentinel here */
/* and do an unconditional assignment instead of testing for nil */
/* instead of checking if x->parent is the root as in the book, we */
/* count on the root sentinel to implicitly take care of this case */
x->parent=y->parent;
if( y == y->parent->left) {
y->parent->left=x;
} else {
y->parent->right=x;
}
x->right=y;
y->parent=x;
#ifdef DEBUG_ASSERT
Assert(!tree->nil->red,"nil not red in RightRotate");
#endif
}
/***********************************************************************/
/* FUNCTION: TreeInsertHelp */
/**/
/* INPUTS: tree is the tree to insert into and z is the node to insert */
/**/
/* OUTPUT: none */
/**/
/* Modifies Input: tree, z */
/**/
/* EFFECTS: Inserts z into the tree as if it were a regular binary tree */
/* using the algorithm described in _Introduction_To_Algorithms_ */
/* by Cormen et al. This funciton is only intended to be called */
/* by the RBTreeInsert function and not by the user */
/***********************************************************************/
void TreeInsertHelp(rb_red_blk_tree* tree, rb_red_blk_node* z) {
/* This function should only be called by InsertRBTree (see above) */
rb_red_blk_node* x;
rb_red_blk_node* y;
rb_red_blk_node* nil=tree->nil;
z->left=z->right=nil;
y=tree->root;
x=tree->root->left;
while( x != nil) {
y=x;
if (1 == tree->Compare(x->key,z->key)) { /* x.key > z.key */
x=x->left;
} else { /* x,key <= z.key */
x=x->right;
}
}
z->parent=y;
if ( (y == tree->root) ||
(1 == tree->Compare(y->key,z->key))) { /* y.key > z.key */
y->left=z;
} else {
y->right=z;
}
#ifdef DEBUG_ASSERT
Assert(!tree->nil->red,"nil not red in TreeInsertHelp");
#endif
}
/* Before calling Insert RBTree the node x should have its key set */
/***********************************************************************/
/* FUNCTION: RBTreeInsert */
/**/
/* INPUTS: tree is the red-black tree to insert a node which has a key */
/* pointed to by key and info pointed to by info. */
/**/
/* OUTPUT: This function returns a pointer to the newly inserted node */
/* which is guarunteed to be valid until this node is deleted. */
/* What this means is if another data structure stores this */
/* pointer then the tree does not need to be searched when this */
/* is to be deleted. */
/**/
/* Modifies Input: tree */
/**/
/* EFFECTS: Creates a node node which contains the appropriate key and */
/* info pointers and inserts it into the tree. */
/***********************************************************************/
rb_red_blk_node * RBTreeInsert(rb_red_blk_tree* tree, void* key, void* info) {
rb_red_blk_node * y;
rb_red_blk_node * x;
rb_red_blk_node * newNode;
x=(rb_red_blk_node*) malloc(sizeof(rb_red_blk_node));
x->key=key;
x->info=info;
TreeInsertHelp(tree,x);
newNode=x;
x->red=1;
while(x->parent->red) { /* use sentinel instead of checking for root */
if (x->parent == x->parent->parent->left) {
y=x->parent->parent->right;
if (y->red) {
x->parent->red=0;
y->red=0;
x->parent->parent->red=1;
x=x->parent->parent;
} else {
if (x == x->parent->right) {
x=x->parent;
LeftRotate(tree,x);
}
x->parent->red=0;
x->parent->parent->red=1;
RightRotate(tree,x->parent->parent);
}
} else { /* case for x->parent == x->parent->parent->right */
y=x->parent->parent->left;
if (y->red) {
x->parent->red=0;
y->red=0;
x->parent->parent->red=1;
x=x->parent->parent;
} else {
if (x == x->parent->left) {
x=x->parent;
RightRotate(tree,x);
}
x->parent->red=0;
x->parent->parent->red=1;
LeftRotate(tree,x->parent->parent);
}
}
}
tree->root->left->red=0;
return(newNode);
#ifdef DEBUG_ASSERT
Assert(!tree->nil->red,"nil not red in RBTreeInsert");
Assert(!tree->root->red,"root not red in RBTreeInsert");
#endif
}
/***********************************************************************/
/* FUNCTION: TreeSuccessor */
/**/
/* INPUTS: tree is the tree in question, and x is the node we want the */
/* the successor of. */
/**/
/* OUTPUT: This function returns the successor of x or NULL if no */
/* successor exists. */
/**/
/* Modifies Input: none */
/**/
/* Note: uses the algorithm in _Introduction_To_Algorithms_ */
/***********************************************************************/
rb_red_blk_node* TreeSuccessor(rb_red_blk_tree* tree,rb_red_blk_node* x) {
rb_red_blk_node* y;
rb_red_blk_node* nil=tree->nil;
rb_red_blk_node* root=tree->root;
if (nil != (y = x->right)) { /* assignment to y is intentional */
while(y->left != nil) { /* returns the minium of the right subtree of x */
y=y->left;
}
return(y);
} else {
y=x->parent;
while(x == y->right) { /* sentinel used instead of checking for nil */
x=y;
y=y->parent;
}
if (y == root) return(nil);
return(y);
}
}
/***********************************************************************/
/* FUNCTION: Treepredecessor */
/**/
/* INPUTS: tree is the tree in question, and x is the node we want the */
/* the predecessor of. */
/**/
/* OUTPUT: This function returns the predecessor of x or NULL if no */
/* predecessor exists. */
/**/
/* Modifies Input: none */
/**/
/* Note: uses the algorithm in _Introduction_To_Algorithms_ */
/***********************************************************************/
rb_red_blk_node* TreePredecessor(rb_red_blk_tree* tree, rb_red_blk_node* x) {
rb_red_blk_node* y;
rb_red_blk_node* nil=tree->nil;
rb_red_blk_node* root=tree->root;
if (nil != (y = x->left)) { /* assignment to y is intentional */
while(y->right != nil) { /* returns the maximum of the left subtree of x */
y=y->right;
}
return(y);
} else {
y=x->parent;
while(x == y->left) {
if (y == root) return(nil);
x=y;
y=y->parent;
}
return(y);
}
}
/***********************************************************************/
/* FUNCTION: InorderTreePrint */
/**/
/* INPUTS: tree is the tree to print and x is the current inorder node */
/**/
/* OUTPUT: none */
/**/
/* EFFECTS: This function recursively prints the nodes of the tree */
/* inorder using the PrintKey and PrintInfo functions. */
/**/
/* Modifies Input: none */
/**/
/* Note: This function should only be called from RBTreePrint */
/***********************************************************************/
void InorderTreePrint(rb_red_blk_tree* tree, rb_red_blk_node* x) {
if (x != tree->nil) {
InorderTreePrint(tree,x->left);
tree->PrintKey(x->key);
InorderTreePrint(tree,x->right);
}
}
/***********************************************************************/
/* FUNCTION: TreeDestHelper */
/**/
/* INPUTS: tree is the tree to destroy and x is the current node */
/**/
/* OUTPUT: none */
/**/
/* EFFECTS: This function recursively destroys the nodes of the tree */
/* postorder using the DestroyKey and DestroyInfo functions. */
/**/
/* Modifies Input: tree, x */
/**/
/* Note: This function should only be called by RBTreeDestroy */
/***********************************************************************/
void TreeDestHelper(rb_red_blk_tree* tree, rb_red_blk_node* x) {
rb_red_blk_node* nil=tree->nil;
if (x != nil) {
TreeDestHelper(tree,x->left);
TreeDestHelper(tree,x->right);
tree->DestroyKey(x->key);
tree->DestroyInfo(x->info);
free(x);
}
}
/***********************************************************************/
/* FUNCTION: RBTreeDestroy */
/**/
/* INPUTS: tree is the tree to destroy */
/**/
/* OUTPUT: none */
/**/
/* EFFECT: Destroys the key and frees memory */
/**/
/* Modifies Input: tree */
/**/
/***********************************************************************/
void RBTreeDestroy(rb_red_blk_tree* tree) {
TreeDestHelper(tree,tree->root->left);
free(tree->root);
free(tree->nil);
free(tree);
}
/***********************************************************************/
/* FUNCTION: RBTreePrint */
/**/
/* INPUTS: tree is the tree to print */
/**/
/* OUTPUT: none */
/**/
/* EFFECT: This function recursively prints the nodes of the tree */
/* inorder using the PrintKey and PrintInfo functions. */
/**/
/* Modifies Input: none */
/**/
/***********************************************************************/
void RBTreePrint(rb_red_blk_tree* tree) {
InorderTreePrint(tree,tree->root->left);
}
/***********************************************************************/
/* FUNCTION: RBExactQuery */
/**/
/* INPUTS: tree is the tree to print and q is a pointer to the key */
/* we are searching for */
/**/
/* OUTPUT: returns the a node with key equal to q. If there are */
/* multiple nodes with key equal to q this function returns */
/* the one highest in the tree */
/**/
/* Modifies Input: none */
/**/
/***********************************************************************/
rb_red_blk_node* RBExactQuery(rb_red_blk_tree* tree, void* q) {
rb_red_blk_node* x=tree->root->left;
rb_red_blk_node* nil=tree->nil;
int compVal;
if (x == nil) return(0);
compVal=tree->Compare(x->key,(int*) q);
while(0 != compVal) {/*assignemnt*/
if (1 == compVal) { /* x->key > q */
x=x->left;
} else {
x=x->right;
}
if ( x == nil) return(0);
compVal=tree->Compare(x->key,(int*) q);
}
return(x);
}
/***********************************************************************/
/* FUNCTION: RBDeleteFixUp */
/**/
/* INPUTS: tree is the tree to fix and x is the child of the spliced */
/* out node in RBTreeDelete. */
/**/
/* OUTPUT: none */
/**/
/* EFFECT: Performs rotations and changes colors to restore red-black */
/* properties after a node is deleted */
/**/
/* Modifies Input: tree, x */
/**/
/* The algorithm from this function is from _Introduction_To_Algorithms_ */
/***********************************************************************/
void RBDeleteFixUp(rb_red_blk_tree* tree, rb_red_blk_node* x) {
rb_red_blk_node* root=tree->root->left;
rb_red_blk_node* w;
while( (!x->red) && (root != x)) {
if (x == x->parent->left) {
w=x->parent->right;
if (w->red) {
w->red=0;
x->parent->red=1;
LeftRotate(tree,x->parent);
w=x->parent->right;
}
if ( (!w->right->red) && (!w->left->red) ) {
w->red=1;
x=x->parent;
} else {
if (!w->right->red) {
w->left->red=0;
w->red=1;
RightRotate(tree,w);
w=x->parent->right;
}
w->red=x->parent->red;
x->parent->red=0;
w->right->red=0;
LeftRotate(tree,x->parent);
x=root; /* this is to exit while loop */
}
} else { /* the code below is has left and right switched from above */
w=x->parent->left;
if (w->red) {
w->red=0;
x->parent->red=1;
RightRotate(tree,x->parent);
w=x->parent->left;
}
if ( (!w->right->red) && (!w->left->red) ) {
w->red=1;
x=x->parent;
} else {
if (!w->left->red) {
w->right->red=0;
w->red=1;
LeftRotate(tree,w);
w=x->parent->left;
}
w->red=x->parent->red;
x->parent->red=0;
w->left->red=0;
RightRotate(tree,x->parent);
x=root; /* this is to exit while loop */
}
}
}
x->red=0;
#ifdef DEBUG_ASSERT
Assert(!tree->nil->red,"nil not black in RBDeleteFixUp");
#endif
}
/***********************************************************************/
/* FUNCTION: RBDelete */
/**/
/* INPUTS: tree is the tree to delete node z from */
/**/
/* OUTPUT: none */
/**/
/* EFFECT: Deletes z from tree and frees the key and info of z */
/* using DestoryKey and DestoryInfo. Then calls */
/* RBDeleteFixUp to restore red-black properties */
/**/
/* Modifies Input: tree, z */
/**/
/* The algorithm from this function is from _Introduction_To_Algorithms_ */
/***********************************************************************/
void RBDelete(rb_red_blk_tree* tree, rb_red_blk_node* z){
rb_red_blk_node* y;
rb_red_blk_node* x;
rb_red_blk_node* nil=tree->nil;
rb_red_blk_node* root=tree->root;
y= ((z->left == nil) || (z->right == nil)) ? z : TreeSuccessor(tree,z);
x= (y->left == nil) ? y->right : y->left;
if (root == (x->parent = y->parent)) { /* assignment of y->p to x->p is intentional */
root->left=x;
} else {
if (y == y->parent->left) {
y->parent->left=x;
} else {
y->parent->right=x;
}
}
if (y != z) { /* y should not be nil in this case */
#ifdef DEBUG_ASSERT
Assert( (y!=tree->nil),"y is nil in RBDelete\n");
#endif
/* y is the node to splice out and x is its child */
if (!(y->red)) RBDeleteFixUp(tree,x);
tree->DestroyKey(z->key);
tree->DestroyInfo(z->info);
y->left=z->left;
y->right=z->right;
y->parent=z->parent;
y->red=z->red;
z->left->parent=z->right->parent=y;
if (z == z->parent->left) {
z->parent->left=y;
} else {
z->parent->right=y;
}
free(z);
} else {
tree->DestroyKey(y->key);
tree->DestroyInfo(y->info);
if (!(y->red)) RBDeleteFixUp(tree,x);
free(y);
}
#ifdef DEBUG_ASSERT
Assert(!tree->nil->red,"nil not black in RBDelete");
#endif
}
/***********************************************************************/
/* FUNCTION: RBDEnumerate */
/**/
/* INPUTS: tree is the tree to look for keys >= low */
/* and <= high with respect to the Compare function */
/**/
/* OUTPUT: stack containing pointers to the nodes between [low,high] */
/**/
/* Modifies Input: none */
/***********************************************************************/
#if(0)
stk_stack* RBEnumerate(rb_red_blk_tree* tree, void* low, void* high) {
stk_stack* enumResultStack;
rb_red_blk_node* nil=tree->nil;
rb_red_blk_node* x=tree->root->left;
rb_red_blk_node* lastBest=nil;
enumResultStack=StackCreate();
while(nil != x) {
if ( 1 == (tree->Compare(x->key,high)) ) { /* x->key > high */
x=x->left;
} else {
lastBest=x;
x=x->right;
}
}
while ( (lastBest != nil) && (1 != tree->Compare(low,lastBest->key))) {
StackPush(enumResultStack,lastBest);
lastBest=TreePredecessor(tree,lastBest);
}
return(enumResultStack);
}
#endif