[TOC]
### 定義
### ADT
### 代碼實現
```
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
struct elt {
struct elt *next;
int value;
};
typedef struct elt *Stack;
#define STACK_EMPTY (0)
void stackPush(Stack *s,int value) {
struct elt *e;
e = malloc(sizeof(* e));
assert(e);
e->value = value;
e->next = *s;
*s = e;
}
int stackEmpty(const Stack *s) {
return (*s == 0);
}
int stackPop(Stack *s) {
int ret;
struct elt *e;
assert(!stackEmpty(s));
ret = (*s)->value;
e = *s;
*s = e->next;
free(e);
return ret;
}
int stackPrint(const Stack *s) {
struct elt *e;
for(e = *s; e!=0;e=e->next) {
printf("%d ",e->value);
}
putchar('\n');
}
//looping over backwords a stack
/*
void
stackPrintReversed(const Stack *s) {
Stack s2;
struct elt *e;
for(e = *s; e!=0;e=e->next) {
stackPush(&s2,e->value);
}
stackPrint(s2);
}
*/
int main(int argc,char **argv) {
int i;
Stack s;
s = STACK_EMPTY;
for(i=0;i<5;i++) {
printf("push %d\n",i);
stackPush(&s,i);
stackPrint(&s);
}
while(!stackEmpty(&s)) {
printf("pop gets %d\n",stackPop(&s));
stackPrint(&s);
}
stackPrintReversed(&s);
return 0;
}
```
