树入门及基本操作代码

/* By Vamei *//* binary search tree */#include <stdio.h>#include <stdlib.h>typedef struct node *position;typedef int ElementTP;struct node {    position parent;    ElementTP element;    position lchild;    position rchild;};/* pointer => root node of the tree */typedef struct node *TREE;void print_sorted_tree(TREE);position find_min(TREE);position find_max(TREE);position find_value(TREE, ElementTP);position insert_value(TREE, ElementTP);ElementTP delete_node(position);static int is_root(position);static int is_leaf(position);static ElementTP delete_leaf(position);static void insert_node_to_nonempty_tree(TREE, position);int main(void){    TREE tr;    position np;    ElementTP element;    tr = NULL;    tr = insert_value(tr, 18);    tr = insert_value(tr, 5);    tr = insert_value(tr, 2);    tr = insert_value(tr, 8);    tr = insert_value(tr, 81);    tr = insert_value(tr, 101);    printf("Original:\n");    print_sorted_tree(tr);    np = find_value(tr, 18000);    if(np != NULL) {        delete_node(np);        printf("After deletion:\n");        print_sorted_tree(tr);    }}/* * print values of the tree in sorted order */void print_sorted_tree(TREE tr){    if (tr == NULL) return;    print_sorted_tree(tr->lchild);    printf("%d \n", tr->element);    print_sorted_tree(tr->rchild);}/* * search for minimum value * traverse lchild */position find_min(TREE tr){    position np;    np = tr;    if (np == NULL) return NULL;    while(np->lchild != NULL) {        np = np->lchild;    }    return np;}/* * search for maximum value * traverse rchild */position find_max(TREE tr){    position np;    np = tr;    if (np == NULL) return NULL;    while(np->rchild != NULL) {        np = np->rchild;    }    return np;}/* * search for value * */position find_value(TREE tr, ElementTP value){    if (tr == NULL) return NULL;    if (tr->element == value) {        return tr;    }    else if (value < tr->element) {        return find_value(tr->lchild, value);    }    else {        return find_value(tr->rchild, value);    }}/* * delete node np */ElementTP delete_node(position np){    position replace;    ElementTP element;    if (is_leaf(np)) {        return delete_leaf(np);    }    else {        /* if a node is not a leaf, then we need to find a replacement */        replace = (np->lchild != NULL) ? find_max(np->lchild) : find_min(np->rchild);        element = np->element;        np->element = delete_node(replace);        return element;    }}/* * insert a value into the tree * return root address of the tree */position insert_value(TREE tr, ElementTP value) {    position np;    /* prepare the node */    np = (position) malloc(sizeof(struct node));    np->element = value;    np->parent  = NULL;    np->lchild  = NULL;    np->rchild  = NULL;    if (tr == NULL) tr = np;    else {        insert_node_to_nonempty_tree(tr, np);    }    return tr;}//=============================================/* * np is root? */static int is_root(position np){    return (np->parent == NULL);}/* * np is leaf? */static int is_leaf(position np){    return (np->lchild == NULL && np->rchild == NULL);}/* * if an element is a leaf, * then it could be removed with no side effect. */static ElementTP delete_leaf(position np){    ElementTP element;    position parent;    element = np->element;    parent  = np->parent;    if(!is_root(np)) {        if (parent->lchild == np) {            parent->lchild = NULL;        }        else {            parent->rchild = NULL;        }    }    free(np);    return element;}/* * insert a node to a non-empty tree * called by insert_value() */static void insert_node_to_nonempty_tree(TREE tr, position np){    /* insert the node */    if(np->element <= tr->element) {        if (tr->lchild == NULL) {            /* then tr->lchild is the proper place */            tr->lchild = np;            np->parent = tr;            return;        }        else {            insert_node_to_nonempty_tree(tr->lchild, np);        }    }    else if(np->element > tr->element) {        if (tr->rchild == NULL) {            tr->rchild = np;            np->parent = tr;            return;        }        else {            insert_node_to_nonempty_tree(tr->rchild, np);        }    }}