题解 | #【模板】栈#

#include <iostream>
#include <string>
using namespace std;

// 因为无法得知操作的数据量，采用链式栈的结构
typedef struct LinkedNode{
    int data;
    struct LinkedNode* next;
}LiStack,*Stack;

void push(Stack &S, int e) {
    Stack T = (Stack)malloc(sizeof(LiStack));
    T -> data = e;
    T -> next = S;
    S = T;
}

int pop(Stack &S) {
    Stack T = S;
    int res = S -> data;
    S = S -> next;
    free(T);
    return res;
}

int top(Stack &S) {
    return S -> data;
}

int main() {
  	// 带头结点的链式栈
    Stack S = (Stack)malloc(sizeof(LiStack));
  	// 初始化
    S -> next = NULL;
    S -> data = 0;
    int a;
    string b;
    int c;
    cin >> a;
    while (a >= 1) {
        cin >> b;
        if(b.compare("push") == 0) {
            cin >> c;
        }
        if(b.compare("push") == 0) {
            // 头插法入栈
            push(S, c);
        } else if(b.compare("pop") == 0) {
            if(S -> next == NULL) {
                cout << "error" << endl;
            } else {
                int res = pop(S);
                cout << res << endl;
            }
        } else if(b.compare("top") == 0) {
            if(S -> next == NULL) {
                cout << "error" << endl;
            } else {
                int res = top(S);
                cout << res << endl;
            }
        }
        a--;
    }

    return 0;
}
// 64 位输出请用 printf("%lld")