栈,即stack,同样是线性表。只是它在设计时,运算规则做了限制。是限定性的线性表结构。
栈,只能在固定的一端插入和取出(取出,也就意味着删除了)。通常,能插入删除的那一端,叫做栈顶,top;不能插入删除的,称为栈底,bottom。插入栈,称为入栈。删除,称为出栈/退栈。当栈中没有元素时,称为空栈。
学习过单片机的应该对栈有了解,毕竟是有一个实实在在的物理容器的概念。出入栈的原则,是先进后出,last in first out(LIFO),因此,栈又被称为,后进先出表。
栈,同样分为顺序栈和链式栈。
如果是顺序栈的话,可能在运算时出现“溢出”。溢出分两种,上溢和下溢。若系统分配的作为栈的储存区满了,还有元素进栈,则是上溢。如果栈里已经没有元素了,还要执行出栈,则是下溢。上溢是一种错误现象,需要分配更大的空间,下溢则常用于作为控制转移的条件或者程序结束的标志。
但是,之前学单片机的经验告诉我,栈是因为在在这么一个特殊的物理结构下呈现的逻辑结构。但不管有没有这样一个物理上的空间结构,编程语言通过算法自己模拟实现了这样的逻辑结构。
一般使用栈,也都是用它的链式结构。所以,程序也只是链式的栈的程序。
首先,是定义一个栈的结构体:
typedef struct node{
elementype data;
struct node *next;
}node,* linkstack;
值得说明的是,在这里设置的栈,是只能在表头插入和删除的单链表。在这种逻辑下,头节点本质上,并不是栈的top。第二个结点,才是栈的top。因为链表的头结点,是链表的寻址由来,是不能被插入和移动的嘛,所以就不能作为真正意义上的top。
各类函数:
elementype popStack(linkstack lstack);
void pushStack(linkstack lstack,elementype DatatoTop);
elementype readTop(linkstack lstack);
void deleteStack(linkstack lstack);
void printDataStack(linkstack lstack);
出栈:
elementype popStack(linkstack lstack)
{
node * tempnode ;//= lstack->next;//= (node *)malloc(sizeof(node));
elementype DataTop = 0;
tempnode = lstack->next;
//tempnode = lstack;
if(tempnode == NULL){
printf("the linkstack is null.\n");
return 0;
}
lstack->next = tempnode->next;
lstack->data--;
printf("the data of top is %d\n",tempnode->data);
DataTop = tempnode->data;
free(tempnode);
return DataTop;
}
入栈(里面的printf函数,是调试用的):
void pushStack(linkstack lstack,elementype DatatoTop)
{
//node * tempnode;
linkstack tempnode;
tempnode = (linkstack)malloc(sizeof(node));
printf("succeed 1\n");
tempnode->data = DatatoTop;
//tempnode->next = NULL;
printf("succeed 2\n");
tempnode->next = lstack->next;
printf("succeed 3\n");
lstack->next = tempnode;
printf("succeed 4\n");
printf("succeed to push %d to stack\n",tempnode->data);
lstack->data++;
}
读top的数据:
elementype readTop(linkstack lstack)
{
node * tempnode ;
elementype DataTop = 0;
tempnode = lstack->next;
if(tempnode == NULL){
printf("the linkstack is null.\n");
return 0;
}
printf("the data of top is %d\n",tempnode->data);
DataTop = tempnode->data;
//这一行要做测试 ,我自己觉得free的话,会把内存free掉的
//free(tempnode);
return DataTop;
}
删除stack:
void deleteStack(linkstack lstack)
{
node * tempnode;
tempnode = lstack->next;
while(tempnode->next != NULL){
tempnode = tempnode->next;
free(tempnode);
lstack->data--;
}
lstack->next = tempnode->next;
free(tempnode);
lstack->data--;
printf("the data of lstack is %d\n",lstack->data);
}
print整个栈:
void printDataStack(linkstack lstack)
{
node * tempnode;
int num = 1;
tempnode = lstack->next;
printf("the data of lstack is %d\n",lstack->data);
while(tempnode->next != NULL){
printf("the data of %d is %d\n",num++,tempnode->data);
tempnode = tempnode->next;
}
printf("the data of %d is %d\n",num++,tempnode->data);
//tempnode = tempnode->next;
}
全部:
#include<stdio.h>
#include<malloc.h>
//#define elementype int
typedef int elementype;
/*
功能设计:
进栈、出栈、查长度、读栈顶元素
*/
typedef struct node{
elementype data;
struct node *next;
}node,* linkstack;
elementype popStack(linkstack lstack);
void pushStack(linkstack lstack,elementype DatatoTop);
elementype readTop(linkstack lstack);
void deleteStack(linkstack lstack);
void printDataStack(linkstack lstack);
int main(void)
{
int DatafromTop = 0;
linkstack lstack;
//linkstack * tempstack ;
lstack = (node*)malloc(sizeof(node));
if(lstack == NULL){
printf("fail to init\n");
}
//下面这行,就是说建立了一个空的链栈,事实上是只有个表头
//(只是一个带头的而已,后面也不会存数据,不过可以计长度hhh),栈头栈底都没有,
lstack->next = NULL;
lstack->data = 0;
printf("succeed to init\n");
pushStack(lstack,23);
pushStack(lstack,22);
pushStack(lstack,21);
printDataStack(lstack);
DatafromTop = popStack(lstack);
printf("the DatafromTop is %d\n",DatafromTop);
DatafromTop = readTop(lstack);
printf("the DataofTop is %d\n",DatafromTop);
printDataStack(lstack);
return 0;
}
elementype popStack(linkstack lstack)
{
node * tempnode ;//= lstack->next;//= (node *)malloc(sizeof(node));
elementype DataTop = 0;
tempnode = lstack->next;
//tempnode = lstack;
if(tempnode == NULL){
printf("the linkstack is null.\n");
return 0;
}
lstack->next = tempnode->next;
lstack->data--;
printf("the data of top is %d\n",tempnode->data);
DataTop = tempnode->data;
free(tempnode);
return DataTop;
}
void pushStack(linkstack lstack,elementype DatatoTop)
{
//node * tempnode;
linkstack tempnode;
tempnode = (linkstack)malloc(sizeof(node));
printf("succeed 1\n");
tempnode->data = DatatoTop;
//tempnode->next = NULL;
printf("succeed 2\n");
tempnode->next = lstack->next;
printf("succeed 3\n");
lstack->next = tempnode;
printf("succeed 4\n");
printf("succeed to push %d to stack\n",tempnode->data);
lstack->data++;
}
elementype readTop(linkstack lstack)
{
node * tempnode ;
elementype DataTop = 0;
tempnode = lstack->next;
if(tempnode == NULL){
printf("the linkstack is null.\n");
return 0;
}
printf("the data of top is %d\n",tempnode->data);
DataTop = tempnode->data;
//这一行要做测试 ,我自己觉得free的话,会把内存free掉的
//free(tempnode);
return DataTop;
}
void deleteStack(linkstack lstack)
{
node * tempnode;
tempnode = lstack->next;
while(tempnode->next != NULL){
tempnode = tempnode->next;
free(tempnode);
lstack->data--;
}
lstack->next = tempnode->next;
free(tempnode);
lstack->data--;
printf("the data of lstack is %d\n",lstack->data);
}
void printDataStack(linkstack lstack)
{
node * tempnode;
int num = 1;
tempnode = lstack->next;
printf("the data of lstack is %d\n",lstack->data);
while(tempnode->next != NULL){
printf("the data of %d is %d\n",num++,tempnode->data);
tempnode = tempnode->next;
}
printf("the data of %d is %d\n",num++,tempnode->data);
//tempnode = tempnode->next;
}
``