数据结构初学————栈的基本操作

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

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

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

void init(PSTACK);
void push(PSTACK, int);
void traverse(PSTACK);
bool pop(PSTACK, int *);
void clear(PSTACK pS);

int main(void)
{
STACK S;//STACK  等价于 struct Stack;
int val;

init( &S);//目的是造出一个空栈
push(&S, 1);//压栈
push(&S, 2);
push(&S, 3);
push(&S, 4);
push(&S, 5);
push(&S, 6);
traverse(&S); //遍历输出

if( pop(&S, &val) )//出栈
{
printf("出栈成功，出栈的元素是%d\n ", val);
}
else
{
printf("出栈失败！\n");
}

traverse(&S);
clear(&S);
traverse(&S);
if( pop(&S, &val) )//出栈
{
printf("出栈成功，出栈的元素是%d\n ", val);
}
else
{
printf("出栈失败！\n");
}

return 0;
}

void init(PSTACK pS)
{
pS->pTop = (PNODE)malloc(sizeof(NODE));
if(NULL == pS->pTop)
{
printf("动态内存分配失败！\n");
exit(-1);
}
else
{
pS->pBottom = pS->pTop;
pS->pTop->pNext = NULL;  //pS->pBottom->pNext = NULL;
}
return;
}

void push(PSTACK pS, int val)
{
PNODE pNew = (PNODE)malloc(sizeof(NODE));
pNew->data = val;
pNew->pNext = pS->pTop; //pS.Top 不能改成pS.pBottom;
pS->pTop = pNew;
return;
}

void traverse(PSTACK pS)
{
PNODE p = pS->pTop;

while(p != pS->pBottom)
{
printf("%d ", p->data);
p = p->pNext;
}
printf("\n");
return;
}

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

//把pS所指向的栈出栈一次，并把出栈的元素存入 pVal形参所指向的变量中 。如果出栈失败，返回 false，否则返回true。
bool pop(PSTACK pS, int *pVal)
{

if(empty(pS))//pS本身存放的就是S的地址
{
return false;
}
else
{
PNODE r = pS->pTop;
*pVal = r->data;
pS->pTop = r->pNext;
free(r);
r = NULL;

return true;
}
}

//clear清空
void clear(PSTACK pS)
{
if(empty(pS))
{
return;
}
else
{
PNODE p = pS->pTop;
PNODE q = NULL;
while(pS ->pBottom != p)
{
q = p ->pNext;
free(p);
p = q;
}
pS ->pTop = pS->pBottom;
}
}