链头 == 栈顶。

#include<iostream>
using namespace std;
// 链栈
typedef int ElemType;
typedef struct Linknode {
  ElemType data;
  struct Linknode *next;
} *LiStack;
// 初始化
void InitLiStack(LiStack &S) {
  S = (LiStack)malloc(sizeof(struct Linknode));
  S->next = NULL;
}
// 入栈
bool PushLiStack(LiStack &S, ElemType x) {
  LiStack p = (LiStack)malloc(sizeof(struct Linknode));
  p->data = x;
  p->next = S->next;
  S->next = p;
  return true;
}
// 出栈
bool PopLiStack(LiStack &S, ElemType &x) {
  if (S->next == NULL) return false;
  LiStack p = S->next;
  x = p->data;
  S->next = p->next;
  free(p);
  return true;
}
// 遍历
void TraverseLiStack(LiStack S) {
  LiStack p = S->next;
  while (p != NULL) {
    cout << p->data << " ";
    p = p->next;
  }
  cout << endl;
}
// 求链栈长度
int StackLength(LiStack S) {
  int length = 0;
  LiStack p = S->next;
  while (p != NULL) {
    length++;
    p = p->next;
  }
  return length;
}
int main() {
  LiStack S;
  ElemType x;
  InitLiStack(S);
  PushLiStack(S, 1);
  PushLiStack(S, 2);
  PushLiStack(S, 3);
  PopLiStack(S, x);
  cout << "出栈元素：" << x << endl;
  TraverseLiStack(S);
  cout << "链栈长度：" << StackLength(S) << endl;
  return 0;
}