C++ 作业

#include <iostream>#include <algorithm>#include <cstring>#include <cstdio>#include <stack>using namespace std;const int INF = 1E9 + 7;class Stack {private :    struct node {        int key;        struct node * pre;        struct node * nexT;    }*tail;    int length;public:    Stack () {        tail = NULL;        length = 0;    }    ~Stack () {        delete tail;    }    void push (int x);    int pop ();    int top ();    inline int size () {return length;}    inline bool empty () {return length == 0;}};void Stack:: push (int x) {    node * temp;    temp = new (node);    tail -> nexT = temp;    temp -> pre = tail;    tail = temp;    temp -> key = x;    tail -> nexT = NULL;}int Stack:: top () {    if (empty()) return INF;    return tail -> key;}int Stack:: pop() {    if (empty()) return INF;    if (size () == 1) {        tail = NULL;        return -INF;    }    node * temp = tail;    tail = tail -> pre;    tail -> nexT = NULL;    int ans = temp -> key;    delete temp;    return ans;}int main () {    return 0;}