栈(stack)--c实现(使用双链表)

是不是直接贴代码不太好，我竟然不知道说什么。

写这个考虑的问题，或者是纠结的问题是这个头指针怎么处理，也就是栈的顶部，最后采用的是初始化第一个栈空间浪费掉，栈顶是有元素的。好像应该去学习下画图，没图不太好说。

写数据结构栈的时候发现自己的2个地方需要进一步补习，用的时候心中没谱---指针和内存分配，看来我还是太水，代码里有3个warning没改出来。

#include <stdio.h>


typedef struct node
{
    int data;
    struct node* next;
    struct node* pre;
}Node;

//Stack 一直指向栈顶
typedef Node* Stack;

void InitStack(Stack* stack);
void DeleteStack(Stack* stack);
int TopStack(Stack*);
void PushStack(Stack* stack, int elem);
int PopStack(Stack *stack);
int IsNull(Stack*);
void PrintStack(Stack *);

void PrintStack(Stack *stack)
{
    Node* preNode = *stack;
    while((preNode->pre != NULL)
          &&preNode)
    {
        printf("%d", preNode->data);
        preNode = preNode->pre;
        if(preNode->pre != NULL){
            printf("<==");
        }
    }
    printf("
");

}
//1 means NULL
//stack-->node-->datamem
//这个地方第一次写传的是Stack stack，为什么报错？因为穿的是值，就是一个copy，pre不能确定一定是NULL
int IsNull(Stack *stack)
{
     return ((*stack)->pre == NULL);
}

int PopStack(Stack *stack)
{
    if(IsNull(stack))
    {
        printf("empty stack.
");
        return -1;
    }
    int popData = -1;
    popData = (*stack)->data;
    Node* popNode = NULL ;
    popNode = *stack;
    *stack = (*stack)->pre;
    (*stack)->pre = popNode->pre->pre;
    (*stack)->next = NULL;

    popNode->pre->pre->next = (*stack);

    free(popNode);//warning

    return popData;
}
void InitStack(Stack* stack)
{
    (*stack)->next = NULL;
    (*stack)->pre = NULL;
    (*stack)->data = -1;
    return ;
}

int TopStack(Stack *stack)
{
    return (*stack)->data;
}

void PushStack(Stack *stack, int elem)
{
    //Node *pushNode = (Node*)malloc(sizeof(Node));
    Node *pushNode = (Node*) malloc(sizeof(Node));//warning
    if(pushNode == NULL)
     {
         printf("malloc error at line %d.", __LINE__);
         return;
     }

    pushNode->data = elem;
    pushNode->next = NULL;
    pushNode->pre = *stack;
    (*stack)->next = pushNode;
    *stack = (*stack)->next;

}

void DeleteStack(Stack* stack)
{

    Node* preNode = stack;
    while((*stack)->pre != NULL)
    {
        PopStack(stack);

    }
    free(*stack);

    return ;
}


int main(void)
{
    printf("Hello World!
");
    Stack *stack =NULL;
    stack = (Stack*)malloc(sizeof(stack));//warning
    *stack = (Node*)malloc(sizeof(Node));
    InitStack(stack);
    IsNull(stack);
    printf("isNull=[%d]
", IsNull(stack));
    printf("the top ele is [%d]
", (*stack)->data);
    printf("push elem  1, 2, 3, 4, 3
");
    PushStack(stack, 1);
    PrintStack(stack);
    PushStack(stack, 2);
    PushStack(stack, 3);
    PushStack(stack, 4);
    PushStack(stack, 3);
    printf("print the curr stack.
");
    PrintStack(stack);
    printf("Pop the stack and print the curr stack.
");
    PopStack(stack);
    PrintStack(stack);

    printf("the top elem is %d
", TopStack(stack));


    return 0;
}

是不是也把运行结果贴上去？？

QT运行的，懒得去开虚拟机在linux跑，太费事，还要改MAKEFILE.

运行结果：/*******************begin

Hello World!
isNull=[1]
the top ele is [-1]
push elem  1, 2, 3, 4, 3
1
print the curr stack.
3<==4<==3<==2<==1
Pop the stack and print the curr stack.
4<==3<==2<==1
the top elem is 4

************end*******/

下一篇写队列吧，想了下定义头尾指针好像会好用点。