数据结构----链式栈（结构体封装与二级指针封装）

        栈代表一种先进后出的存储方式，在实际应用中，基本上有回退操作的都需要运用到栈。

一个栈需要实现的基本操作有：入栈 出栈和标记栈顶元素。 由于这种先进后出的存储结构和链表的头插法非常的相似，所以我们可以借鉴头插法写出一个链式栈。

以下是链式栈的具体代码（通过结构体再封装实现）

#include<stdio.h>
#include <stdlib.h>
//栈：先进后出。   所有关于回退问题的都需要用到栈。
/*栈的基本操作：入栈
出栈
标记栈顶元素
由于栈是先进后出 ，类似于链表的头插法，所以可以使用链式结构来实现*/

typedef struct _Node{    //栈中存放_Node类型的数据
	int data;
	struct _Node* next;
}Node;
typedef struct _Stack{
	int stackSize;              //表示栈中元素的个数
	Node* stackTop;				//Node类型指针 指向栈顶元素
}stack;

Node* createNode(int data){						//新建节点
	Node* newNode = (Node*)malloc(sizeof(Node));
	newNode->data = data;
	newNode->next = NULL;
	return newNode;
}
stack* createStack(){							 //初始化一个栈
	stack* pStack = (stack*)malloc(sizeof(stack));
	pStack->stackSize = 0;
	pStack->stackTop = NULL;
	return pStack;
}
int isEmpty(stack* pstack){						//判断栈是否为空
	if (pstack->stackSize)
		return 1;
	else
		return 0;
}
int stackSize(stack* pstack){					//求栈长度
	return pstack->stackSize;
}

void putStack(stack* pstack, int data){        //入栈
	Node* newNode = createNode(data);
	newNode->next = pstack->stackTop;
	pstack->stackTop = newNode;
	pstack->stackSize++;
}

void outStack(stack* pstack){				//出栈
	Node* tempNode = pstack->stackTop;
	pstack->stackTop = pstack->stackTop->next;
	free(tempNode);
	tempNode = NULL;
	pstack->stackSize--;
}

void printStack(stack* pstack){				//打印栈中元素
	while (pstack->stackSize != 0){
		printf("%d ", pstack->stackTop->data);
		pstack->stackTop = pstack->stackTop->next;
	}
}
int main(){
	stack *pstack = createStack();
	putStack(pstack, 10);
	putStack(pstack, 20);
	putStack(pstack, 30);
	outStack(pstack);
	printStack(pstack);
	return 0;

}

下面是二级指针封装的链式栈

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

typedef struct _stackNode{
	int data;
	struct _Node* next;
}stackNode;

stackNode* createStack(int data){
	stackNode* newNode = (stackNode*)malloc(sizeof(stackNode));
	newNode->data = data;
	newNode->next = NULL;
	return newNode;
}
void pushStackNode(stackNode** pstackNode, int data){
	stackNode* newNode = createStack(data);
	newNode->next = (*pstackNode);
	*pstackNode = newNode; 
}
void outStackNode(stackNode** pstackNode){
	if (pstackNode == NULL){
		printf("栈为空，无法输出！\n");
	}
	else{
		stackNode* tempNode = *pstackNode;
		*pstackNode = (*pstackNode)->next;
		free(tempNode);
		tempNode = NULL;
	}
}
void printStack(stackNode* pstackNode){
	stackNode* pMoveNode = pstackNode;
	while (pMoveNode != NULL){
		printf("%d ", pMoveNode->data);
		pMoveNode = pMoveNode->next;
	}
	printf("\n");
}
int main(){
	stackNode* pstackNode = NULL;
	pstackNode=createStack(10);
	pushStackNode(&pstackNode,20);
	pushStackNode(&pstackNode, 30);
	pushStackNode(&pstackNode, 40);
	outStackNode(&pstackNode);
	printStack(pstackNode);
	pushStackNode(&pstackNode, 1000);

	printStack(pstackNode);
}