队列 FIFO

#include <iostream>using namespace std;typedef double T;class List{struct Node{T data;Node* next;Node(const T& t=T()):data(t){next = NULL;}};Node* head;public:List():head(NULL){}void clear(){while(head != NULL){Node* q = head->next;delete head;head = q;}}~List(){clear();}void insert_front(const T& t){Node* p = new Node(t);p->next= head;head = p;}void insert_back(const T& t){Node* p = new Node(t);if (head==NULL)head = p;else{get_pointer(size()-1)->next = p;}}void travel(){Node* p=head;while(p != NULL){cout << p->data << ' ';p = p->next; }cout << endl;}int size(){int cnt = 0;Node* p = head;while(p != NULL){cnt++;p = p->next;}return cnt;}T get_head(){if (head == NULL){throw "no head";}return head->data;}T get_tail(){if (head == NULL)throw "no tail";Node* p = head;while(p->next != NULL){p = p->next;}return p->data;}bool empty(){return head == NULL;}int find(const T& t){int pos = 0;Node* p = head;while(p != NULL){if (p->data== t)return pos;p = p->next;pos++;}return -1;}bool update(const T& o, const T& n){int pos = find(o);if (pos == -1)return false;Node* p = get_pointer(pos);p->data = n;return true;}private:Node* get_pointer(int pos){Node* p = head;for (int i=0; i<pos; i++)p = p->next;return p;}public:bool erase(const T& t){int pos = find(t);if (pos == -1)return false;if (pos ==0){Node* q = head->next;delete head;head = q;}else{Node* pre = get_pointer(pos-1);Node *cur = pre->next;pre->next= cur->next;delete cur;}}};class Queue{List l;public:void push(const T& t)  //数据入队列 {l.insert_back(t);}void pop()  //删除队首元素 {l.erase(l.get_head());}T front()  //取得队列首元素{return l.get_head();} T back()//取得队列尾元素{return l.get_tail();} bool empty()  //判断队列是否为空 {return l.empty();} int size()//取得队列中的元素个数{return l.size();} void clear()//清空整个队列{l.clear();} };int main(){Queue q;q.push(1.0);q.push(2.0);q.push(3.0);q.push(4.0);q.push(5.5);cout.setf(ios::showpoint);  //格式化输出，带小数部分 while(!q.empty()){cout << q.front() << ' ';q.pop();}cout << endl;return 0;}