二叉排序树

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#include <stdio.h>#include <stdlib.h>//二叉排序树结点typedef struct BSTreeNode {    int val;    struct BSTreeNode *lchild;    struct BSTreeNode *rchild;} BSTreeNode, *BSTree;BSTree insert(BSTree root, int val) {    if (root == NULL) {        BSTree node = (BSTree) malloc(sizeof(BSTreeNode));        node->val = val;        node->lchild = NULL;        node->rchild = NULL;        root = node;    }    else if (val < root->val) {        root->lchild = insert(root->lchild, val);    }    else {        root->rchild = insert(root->rchild, val);    }    return root;}BSTree buildBSTree(BSTree root, int *arr, int n) {    int i;    for (i = 0; i < n; i++) {        root = insert(root, arr[i]);    }    return root;}//查找元素key,找到返回key的结点指针，没找到返回NULLBSTree search(BSTree root, int key) {    if (root == NULL) {        return NULL;    }    if (key > root->val)//查找右子树    {        return search(root->rchild, key);    }    else if (key < root->val)//查找左子树    {        return search(root->lchild, key);    }    else {        return root;    }}int delNode(BSTree *root) {    BSTree q, s;    //root为叶子结点    if (!(*root)->lchild && !(*root)->rchild) {        *root = NULL;    }    else if (!(*root)->lchild) {//左子树为空，重接右子树        q = *root;        *root = (*root)->rchild;        free(q);    } else if (!(*root)->rchild) {//右子树为空，重接左子树        q = *root;        *root = (*root)->rchild;        free(q);    } else {//左右子树均不为空        q = *root;        s = (*root)->lchild;        while (s->rchild) {            q = s;            s = s->rchild;//转左，然后向右走到尽头        }        (*root)->val = s->val;        if (q != *root) {//判断是否执行上述while循环            q->rchild = s->lchild;//执行上述while循环，重接右子树        } else {            q->lchild = s->lchild;//未执行上述while循环，重接左子树        }        free(s);    }    return 1;}//若二叉排序树T中存在关键字等于key的数据元素时，则删除该数据元素结点int delBST(BSTree *root, int key) {    if (!(*root)) {        return 0;    }    else {        if (key == (*root)->val) {            return delNode(root);        } else if (key < (*root)->val) {            return delBST(&(*root)->lchild, key);        } else {            return delBST(&(*root)->rchild, key);        }    }}void visit(BSTree root) {    printf("%d ", root->val);}//前序遍历void preOrder(BSTree root) {    if (root != NULL) {        visit(root);//访问根结点        preOrder(root->lchild);        preOrder(root->rchild);    }}//中序遍历void inOrder(BSTree root) {    if (root != NULL) {        inOrder(root->lchild);        visit(root);        inOrder(root->rchild);    }}//后序遍历void postOrder(BSTree root) {    if (root != NULL) {        postOrder(root->lchild);        postOrder(root->rchild);        visit(root);    }}int main() {    int arr[] = {10, 6, 15, 2, 7, 12, 4, 13};    BSTree root = NULL;    root = buildBSTree(root, arr, 8);    printf("先序遍历二叉树: ");    preOrder(root);    printf("\n");    /*printf("中序遍历二叉树: ");    inOrder(root);    printf("\n");    printf("后序遍历二叉树: ");    postOrder(root);    printf("\n");*/    //查找元素7    /*BSTree node = search(root,7);    if (node != NULL){        printf("二叉排序树存在结点值为%d的结点\n",node->val);    } else {        printf("二叉排序树不存在结点值为7的结点\n");    }*/    /*//查找元素25    BSTree node1 = search(root,25);    if (node1 != NULL){        printf("二叉排序树存在结点值为%d的结点\n",node1->val);    } else {        printf("二叉排序树不存在结点值为25的结点\n");    }*/    if (delBST(&root,2)) {        printf("删除结点元素为2的结点\n先序遍历二叉树: ");        preOrder(root);    }    return 0;}
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