栈的动态实现

/节点
typedef struct Node{
int data;
struct Node *pNext;
}NODE,*PNODE;

//栈
typedef struct Stack{
PNODE pTop;
PNODE pBottom;
}STACK,*PSTACK;

void init(PSTACK pStack){
//分配内存
pStack->pTop=(PNODE)malloc(sizeof(NODE));

if(NULL==pStack->pTop){
printf("动态分配内存失败");
exit(-1);
}else{
//初始化，没有数据在栈中时，栈顶和栈底都指向同一方向
//然后是栈底中的指针域设置为空
pStack->pBottom=pStack->pTop;
pStack->pBottom->pNext=NULL;
}
}

void push(PSTACK pStack,int val)
{
//分配新节点
PNODE pNew=(PNODE)malloc(sizeof(NODE));
//为新的节点赋值
pNew->data=val;
//将新节点的指针域指向栈顶
pNew->pNext=pStack->pTop;
//将栈顶指向pNew
pStack->pTop=pNew;

return;

}

bool pop(PSTACK pStack,int *pVal){
//判断栈是否为空
if(is_empty(pStack)){
return false;
}else{
//分配临时的 PNODE，用来保存栈顶
PNODE temp=pStack->pTop;
//将出栈的元素保存起来
*pVal=temp->data;
//将栈顶指向下一个 PNODE
pStack->pTop=temp->pNext;
//释放临时
free(temp);
temp=NULL;
return true;
}
}

bool is_empty(PSTACK pStack){
if(pStack->pTop==pStack->pBottom)
return true;
else
return false;
}

void traverse(PSTACK pStack){
//定义一个临时PNODE,不改变栈顶和栈底
if(is_empty(pStack)){
printf("栈没有元素！");
}
PNODE p=pStack->pTop;
while(p!=pStack->pBottom){
printf("%d ",p->data);
p=p->pNext;
}
printf("\n");
}

void clear(PSTACK pStack){
//判断栈是否为空
if(is_empty(pStack))
return;

else{
//先从栈顶
PNODE p=pStack->pTop;
PNODE q=NULL;
//p q上下交替相互赋值
while(p!=pStack->pBottom){
q=p->pNext;
free(p);
p=q;
}
//使栈顶等于栈底
pStack->pTop=pStack->pBottom;
}
}

#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>

//方法声明
void init(PSTACK pStack);
void push(PSTACK pStack,int val);
void traverse(PSTACK pStack);
bool pop(PSTACK pStack,int *pVal);
bool is_empty(PSTACK pStack);
void clear(PSTACK pStack);

int main()
{
STACK s;//STACK等价于struct Stack;
int pVal;
//初始化
init(&s);
//入栈
push(&s,2);
push(&s,1);
push(&s,3);
push(&s,1);
push(&s,5);
push(&s,1);
//遍历
traverse(&s);
pop(&s,&pVal);
traverse(&s);
printf("出栈的元素是pVal=%d\n",pVal);
clear(&s);
traverse(&s);
}