指针作为形式参数时 改变指针所指的值（二叉排序树）

例题一：让原本指向空的两个指针，赋值

<wbr><span style="font-size:18px"><strong>#include"stdio.h"</strong></span> <div><span style="font-size:18px"><strong>#include"malloc.h"</strong></span></div> <div><span style="font-size:18px"><strong>#include"string.h"</strong></span></div> <div><span style="font-size:18px"><strong>void TestFunction(char** ptr1, char*&amp; ptr2)//我经常喜欢用 *&amp;ptr2</strong></span></div> <div><span style="font-size:18px"><strong>{</strong></span></div> <div><span style="font-size:18px"><strong>*ptr1 = "abc";</strong></span></div> <div><span style="font-size:18px"><strong>ptr2 = (char*)malloc(6);</strong></span></div> <div><span style="font-size:18px"><strong>strcpy(ptr2, "abc");</strong></span></div> <div><span style="font-size:18px"><strong>}</strong></span></div> <div><span style="font-size:18px"><br><strong></strong></span></div> <div><span style="font-size:18px"><strong>int main()</strong></span></div> <div><span style="font-size:18px"><strong>{</strong></span></div> <div><span style="font-size:18px"><strong>char* ptr1 = NULL, *ptr2 = NULL;</strong></span></div> <div><span style="font-size:18px"><strong>TestFunction(&amp;ptr1, ptr2);</strong></span></div> <div><span style="font-size:18px"><strong>printf("%s\n", ptr1);</strong></span></div> <div><span style="font-size:18px"><strong>printf("%s\n", ptr2);</strong></span></div> <div><span style="font-size:18px"><strong>free(ptr2);</strong></span></div> <div><span style="font-size:18px"><strong>}</strong></span></div> </wbr>

例题二：二叉排序树的实现

#include"stdio.h"

#include"malloc.h"

struct node

{

int data;

node *right;

node *left;

};

void insert(node *&root,node *&s)//传递的参数是关键

{

if(root==NULL)

{

root=s;

}

else

{

if(root->data<s->data)//要插入的数据 data大于节点 则插入右边

insert(root->right,s);

else

insert(root->left,s);

}

}

void creatTree(node *&root,int a[],int n)

{

int i;

node *s;

//root=(node*)malloc(sizeof(node));//不要在这里初始化 或者申请空间之后 root=NULL;

for(i=0;i<n;i++)

{

s=(node *)malloc(sizeof(node));

s->data=a[i];

s->right=NULL;

s->left=NULL;

insert(root,s);

}

}

void outPut(node *&root)

{

if(root==NULL)

return;

else

{

outPut(root->left);

printf("%5d",root->data);

outPut(root->right);

}

}

int main()

{

int a[]={15,2,4,6,7,13,9,3,17,18,20};

node *root;

root=(node*)malloc(sizeof(node));//（申请空间大小）

root=NULL;//这一句一定不能少 （初始化）

creatTree(root,a,11);

outPut(root);

return 0;

}