《c和指针》笔记-简洁的二叉查找树删除node方法

之前写过一个二叉查找树，其中最麻烦的是删除元素的方法，一共分了8种情况，主要是要区分是否是根节点和非根节点，

写的太烦了，详细请参见：http://blog.csdn.net/todd911/article/details/8471566

今天要来简化一下这个方法，之前我还写过一篇《简洁的单项链表插入操作》，利用双指针，简化了根节点和非根节点的区别，

详细请参见：http://blog.csdn.net/todd911/article/details/8941593，其实在二叉查找树中也可以使用这种方法。

改进后的代码如下：

void deleteNode(treeNode** node, int value){        treeNode* current;        while( (current = *node) != NULL && current->value != value ){                if(current->value > value){                        node = ¤t->left;                }else if(current->value < value){                        node = ¤t->right;                }        }//如果current为NULL，则没有找到        if(current == NULL){                printf("this node want to delete is not exit!\n");        }else{//如果找到节点，则判断节点的状态//没有孩子节点，则直接删除                if(current->left == NULL && current->right == NULL){                        free(current);                        *node = NULL;                        current = NULL;                }else //左右孩子都有，则先将右孩子插入到左孩子树上，再将原先指向current的指针指向current的左孩子，删除currentif(current->left != NULL && current->right != NULL){                        insertNode(current->left, current->right);                        *node = current->left;                        free(current);                        current = NULL;                }else //没有左孩子，有右孩子，则将原先指向current的指针指向current的右孩子，删除currentif(current->left == NULL && current->right != NULL){                        *node = current->right;                        free(current);                        current = NULL;                }else //没有右孩子，有左孩子，则将原先指向current的指针指向current的左孩子，删除currentif(current->left != NULL && current->right == NULL){                        *node = current->left;                        free(current);                        current = NULL;                }        }}

这种方法有一个问题，就是被删除的节点都有左右孩子，就会先将右孩子插入到左孩子树上，再将原先指向current的指针指向current的左孩子，

导致二叉树的树干长度不平衡了。

详细步骤如下，节点12是要被删除的：

可见，最后树的结构破坏比较大， 可能会导致查找的效率降低。

下面我们来改进一下，如果要被删除的节点有左右孩子，则从左孩子获得值最大的那个，来替换要被删除的节点，详细步骤如下，节点12是要被删除的：

怎么样，树的结构没有怎么被破坏吧，推荐还是使用这种方法比较好。

下面附上完整的sample代码：

#include <stdio.h>#include <stdlib.h>#define SIZE 10typedef struct tagNode{        int value;        struct tagNode* left;        struct tagNode* right;}treeNode;void displayArray(int array[],int size){        printf("the array is:");        int i;        for(i=0;i<size;i++){                printf("%d ",array[i]);        }        printf("\n");}void displayTree(treeNode* node){        if(node == NULL) return;        if(node->left != NULL){                displayTree(node->left);        }        printf("%d ",node->value);        if(node->right != NULL){                displayTree(node->right);        }}void insertNode(treeNode* node, treeNode* iNode){        if(iNode->value >= node->value && node->right != NULL){                insertNode(node->right, iNode);                return;        }        if(iNode->value < node->value && node->left != NULL){                insertNode(node->left, iNode);                return;        }        if(iNode->value >= node->value && node->right == NULL){                node->right = iNode;        }        if(iNode->value < node->value && node->left == NULL){                node->left = iNode;        }}void deleteNode(treeNode** node, int value){        treeNode* current;        while( (current = *node) != NULL && current->value != value ){                if(current->value > value){                        node = ¤t->left;                }else if(current->value < value){                        node = ¤t->right;                }        }        if(current == NULL){                printf("this node want to delete is not exit!\n");        }else{                if(current->left == NULL && current->right == NULL){                        free(current);                        *node = NULL;                        current = NULL;                }else if(current->left != NULL && current->right != NULL){                        insertNode(current->left, current->right);                        *node = current->left;                        free(current);                        current = NULL;                }else if(current->left == NULL && current->right != NULL){                        *node = current->right;                        free(current);                        current = NULL;                }else if(current->left != NULL && current->right == NULL){                        *node = current->left;                        free(current);                        current = NULL;                }        }}void getMaxValueNode(treeNode **link){        while( *link != NULL && (*link)->right != NULL){                *link = (*link)->right;        };}void deleteNode2(treeNode** node, int value){        treeNode* current;        while( (current = *node) != NULL && current->value != value ){                if(current->value > value){                        node = ¤t->left;                }else if(current->value < value){                        node = ¤t->right;                }        }        if(current == NULL){                printf("this node want to delete is not exit!\n");        }else{                if(current->left == NULL && current->right == NULL){                        free(current);                        *node = NULL;                        current = NULL;                }else if(current->left != NULL && current->right != NULL){                        treeNode** link = ¤t->left;                        getMaxValueNode(link);                        if(*link != NULL){                                treeNode *maxValueNode = *link;                                *link = (*link)->left;                                maxValueNode->left = current->left;                                maxValueNode->right = current->right;                                *node = maxValueNode;                                free(current);                                current = NULL;                        }                }else if(current->left == NULL && current->right != NULL){                        *node = current->right;                        free(current);                        current = NULL;                }else if(current->left != NULL && current->right == NULL){                        *node = current->left;                        free(current);                        current = NULL;                }        }}void createTree(treeNode** root, int array[], int size){        int i;        *root = (treeNode*)malloc(sizeof(treeNode));        (*root)->value = array[0];        (*root)->left = NULL;        (*root)->right = NULL;        for(i=1;i<size;i++){                treeNode* child = (treeNode*)malloc(sizeof(treeNode));                child->value = array[i];                child->left = NULL;                child->right = NULL;                insertNode(*root, child);        }}void deleteTree(treeNode* node){        if(node == NULL) return;        if(node->left != NULL){                deleteTree(node->left);        }        if(node->right != NULL){                deleteTree(node->right);        }        if(node->left == NULL && node->right == NULL){                free(node);                node = NULL;        }}int main(int argc, char* argv[]){        int array[SIZE] = {60,4,45,78,345,23,12,3,6,21};        displayArray(array,SIZE);        treeNode *root = NULL;        createTree(&root, array, SIZE);        printf("the tree is(left->middle->right):");        displayTree(root);        printf("\n");        int value = 12;        printf("delete value:%d\n",value);        deleteNode(&root,value);        printf("the tree is(left->middle->right):");        displayTree(root);        printf("\n");        value = 78;        printf("delete value:%d\n",value);        deleteNode2(&root,value);        printf("the tree is(left->middle->right):");        displayTree(root);        printf("\n");        deleteTree(root);        return 0;}