二叉树的建立并输出
#include <stdio.h>
#include <stdlib.h>

struct node{
int value;
struct node *child_l;
struct node *child_r;
};

int add_node(struct node **pointer, struct node *new_node);

struct node *create_node(int data)
{
struct node *new_node = NULL;
struct node **pointer = NULL;

new_node = (struct node *)malloc(sizeof(struct node));
new_node -> value = data;
new_node -> child_l = NULL;
new_node -> child_r = NULL;
add_node(pointer, new_node);

return new_node;
}

int add_node(struct node **pointer, struct node *new_node)
{
if(*pointer == NULL)
{
*pointer = new_node;
}
else
{
if((*pointer) -> value > new_node-> value)
add_node(&(*pointer) -> child_l, new_node);
else
add_node(&(*pointer) -> child_r, new_node);
}
return 0;
}

int main()
{
struct node *new_node;
int i;
int A[12] = {3,31,45,47,51,58,67,72,78,85,99,105};

for(i=0; i <12; i++){
new_node = create_node(A[i]);
printf( "the tree: %d ", new_node -> value);
}
return 0;
}
=======================================================================
编译通过了, 就是一运行会出错,哪位高手指点下,谢谢了!!



[解决办法]
struct node *create_node(int data
+PtNode root
)
{
struct node *new_node = NULL;
struct node **pointer = NULL;

new_node = (struct node *)malloc(sizeof(struct node));
+ if(new_node==NULL){
destoryTree(root);
exit(-1);
}
new_node -> value = data;
new_node -> child_l = NULL;
new_node -> child_r = NULL;
add_node(pointer, new_node);

return new_node;
}

[解决办法]
struct node{
int value;
struct node *child_l;
struct node *child_r;
};

int add_node(struct node **pointer, struct node *new_node);

struct node *create_node(struct node **head, int data)
{
struct node *new_node = NULL;

new_node = (struct node *)malloc(sizeof(struct node));
new_node -> value = data;
new_node -> child_l = NULL;
new_node -> child_r = NULL;
add_node(head, new_node);

return new_node;
}

int add_node(struct node **head, struct node *new_node)
{
if(*head == NULL)
{
*head = new_node;
}
else
{
if((*head)-> value > new_node-> value)
add_node(&(*head)-> child_l, new_node);
else
add_node(&(*head)-> child_r, new_node);
}
return 0;
}


int main(int argc, char *argv[])
{
struct node *new_node, *head=NULL;
int i;
int A[12] = {3,31,45,47,51,58,67,72,78,85,99,105};

for(i=0; i <12; i++){
new_node = create_node(&head, A[i]);
printf( "the tree: %d ", new_node-> value);
}
return 0;
}
[解决办法]
if(*pointer == NULL)／／程序运行到这里报错，原因在于下面的赋值语句
　　　　　struct node **pointer = NULL;／／这里说明二重指针指向一个ＮＵＬＬ，那么上面语句＊pointer＝＊ＮＵＬＬ，所以出错了
struct node **pointer = NULL;／／如果把这个改为struct node *pointer = NULL;
调用add_node(pointer, new_node);时，这样调用add_node(＆pointer, new_node);
整理一下也就是把add_node（）函数修改如下，就解决问题了：
struct node *create_node(int data)
{
struct node *new_node = NULL;
struct node *pointer = NULL;

new_node = (struct node *)malloc(sizeof(struct node));
new_node -> value = data;
new_node -> child_l = NULL;
new_node -> child_r = NULL;
add_node(&pointer, new_node);

return new_node;
}