#include <stdio.h>

#include <stdlib.h>

typedef int ElemType;

typedef struct StackNode{

    ElemType data;

    struct StackNode *next;

}StackNode;

StackNode *InitStack(StackNode *S);//初始化

StackNode * DestroyStack(StackNode*S);//销毁

void ClearStack(StackNode*S);//清空

int StackEmpty(StackNode*S);//判空

int StackLength(StackNode*S);//栈长度

ElemType GetTop(StackNode*S);//获取栈顶元素，不修改指针位置

StackNode *Push(StackNode*S, ElemType e);//插入栈顶

StackNode *Pop(StackNode *S, ElemType *e);//删除栈顶

void StackTraverse(StackNode *S);//从栈顶依次遍历

//初始化

StackNode *InitStack(StackNode *S){

    S = NULL;

    printf("初始化成功\n");

    return S;

}

//销毁,返回空指针给S

StackNode *DestroyStack(StackNode*S){

    StackNode *p = S->next;

    while(p){

        free(S);

        S = p;

        p = p->next;

    }

    printf("销毁成功\n");

    return NULL;

}

//清空

void ClearStack(StackNode*S){

    printf("清空\n");

    StackNode *p = S;

    while(p!=NULL){

        p->data = ;

        p = p->next;

    }

    printf("清空成功\n");

}

//判空

int StackEmpty(StackNode*S);

//栈长度

int StackLength(StackNode*S){

    int len = ;

    StackNode *p = S;

    while(p!=NULL){

        len++;

        p = p->next;

    }

    return len;

}

//获取栈顶元素，不修改指针位置

ElemType GetTop(StackNode*S){

    if(S!=NULL){

        printf("栈顶元素为%d", S->data);

        return S->data;

    }else{

        printf("空链栈无栈顶元素\n");

        return NULL;

    }

}

//插入栈顶,返回指针指向当前栈顶

StackNode *Push(StackNode*S, ElemType e){

    StackNode *p = NULL;

    p = (StackNode *)malloc(sizeof(StackNode));

    p->data = e;

    p->next = S;

    S = p;

    printf("%d入栈成功\n", e);

    return S;

}

//删除栈顶,返回指针指向当前栈顶

StackNode *Pop(StackNode *S, ElemType *e){

    StackNode *p = NULL;//用于暂存删除元素

    if(S == NULL){

        printf("空链栈，删除失败\n");

        return NULL;

    }

    *e = S->data;

    p = S;

    S = S->next;

    free(p);

    printf("%d出栈成功\n",*e);

    return S;

}

//从栈顶依次遍历

void StackTraverse(StackNode *S){

    StackNode *p = S;

    if(p == NULL){

        printf("空链栈\n");

        return;

    }

    while(p != NULL){

        printf("%d ", p->data);

        p = p->next;

    }

    printf("\n");

}

int main(void){

    StackNode *S;

    ElemType e;

    //初始化测试

    S = InitStack(S);

//    //获取栈顶元素测试

//    GetTop(S);

//    S = Push(S, 999);

//    GetTop(S);

    //入栈测试

    S = Push(S, );

    S = Push(S, );

    S = Push(S, );

    S = Push(S, );

    S = Push(S, );

    //栈长测试

    printf("栈长%d\n",StackLength(S));

    //遍历测试

    StackTraverse(S);

//    //出栈测试

//    S = Pop(S, &e);

//    S = Pop(S, &e);

//    S = Pop(S, &e);

//    //printf("测试e是否改变: %d\n",e);

//    S = Pop(S, &e);

//    StackTraverse(S);

//    //清空测试

//    ClearStack(S);

//    StackTraverse(S);

////    //销毁测试

//    S = DestroyStack(S);

//    StackTraverse(S);

    return ;

}