题解 | #【模板】栈#

#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <vector>
using namespace std;
//结点结构体
typedef int DataType;
typedef struct Node
{
    DataType data;
    struct Node* next;
}Node;

typedef struct Node* LinkStack;
//创建带头结点的链栈
LinkStack CreateStack()
{
    LinkStack top = (Node*)malloc(sizeof(Node));
    top->next = NULL;
    return top;
}
//链栈判空
int isNullStack(LinkStack st)
{
    return st->next == NULL;
}
//入栈
void push(LinkStack* top, DataType data)
{
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    newNode->next = (*top)->next;
    (*top)->next = newNode;
}
//出栈
int pop(LinkStack* top)
{
    int ret;
    if (isNullStack(*top))
        return 0;
    ret = (*top)->next->data;
    Node* temp;
    temp = *top;
    *top = (*top)->next;
    free(temp);
    return ret;
}
//取栈顶元素
int top(LinkStack* top)
{
    if (isNullStack(*top))
        return 0;
    return (*top)->next->data;
}

int main() {
    LinkStack mystack = CreateStack();
    vector<int>ret;
    int data;
    int n;
    char op[256] = { 0 };
    scanf("%d",&n);
    for (int i = 0; i < n; i++)
    {
        cin >> op;
        if (!strcmp(op, "push"))
        {
            scanf("%d", &data);
            push(&mystack, data);
        }

        if (!strcmp(op, "pop"))
            ret.push_back(pop(&mystack));

        if (!strcmp(op, "top"))
            ret.push_back(top(&mystack));
    }
   //输出结果
    for (int i = 0; i < ret.size(); i++)
    {
        if (ret[i] == 0)
            cout << "error" << endl;
        else
            cout << ret[i] << endl;
    }


}