2.2 链栈

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

typedef  struct _Node{
    char data;
    struct _Node *next;
}Node;

typedef struct _Stack{
    Node * top;
}Stack;

void initStack(Stack *s){
    s->top = (Node*)malloc(sizeof(Node));  // 这里的链栈具有头节点，严蔚敏书没有头节点（可以有）
    s->top->next = NULL;
}

int isStackEmpty(Stack *s){
    return s->top->next == NULL;
}

void push(Stack *s, char ch){
    Node * cur = (Node*)malloc(sizeof(Node));
    cur->data = ch;

    cur->next = s->top->next;               // 头插法建立链栈，top指向新插入的地方，便于弹栈
    s->top->next = cur;
}

char pop(Stack *s){
    Node * t = s->top->next;
    char ch = t->data;
    s->top->next = t->next;
    free(t);
    return ch;
}

void resetStack(Stack *s){
    while(!isStackEmpty(s))
        pop(s);
}

void clearStack(Stack *s){
    resetStack(s);
    free(s->top);
}

void dispStack(Stack *s){
    Node *p=s->top->next;
    int i=0;
    while(p){
        printf("%c ",p->data);
        p=p->next;
        i++;
    }
    printf("\nStack Length:%d\n",i);
}


int main(){
    Stack  s;
    initStack(&s);

    for(char ch = 'A'; ch <='Z'; ch++)
    {
        push(&s,ch);
    }

    //resetStack(&s);
    
    dispStack(&s);

    while(!isStackEmpty(&s))
    {
        printf("%c ",pop(&s));
    }

    clearStack(&s);

    return 0;
}