数据结构：Deuque

#include <iostream>
#include <stdio.h>
#include <string>
using namespace std;

struct DequeNode
{
    int Data;
    //无论是插入或者删除都需要更新prev next
    DequeNode* prev;
    DequeNode* next;
    DequeNode() {
        prev = nullptr;
        next = nullptr;
        Data = 0;
    }
    DequeNode* CreateNextNode(int val) {
        DequeNode* node = new DequeNode();
        node->prev = this;
        this->next = node;
        node->Data = val;
        return node;
    }
    DequeNode* CreatePrevNode(int val) {
        DequeNode* node = new DequeNode();
        node->next = this;
        this->prev = node;
        node->Data = val;
        return node;
    }
};
//再出站的时候会导致Min不准确
class Deque
{
public:
    Deque() {
        head = nullptr;
        tail = nullptr;
        size = minVal = 0;
    }
    void push_back(int val)
    {
        if (tail == nullptr)
        {
            tail = new DequeNode();
            tail->Data = val;
            head = tail;
            minVal = val;
            size++;
        }
        else {
            tail = tail->CreateNextNode(val);
            /*tail->next = new DequeNode();
            tail->next->Data = val;
            tail->next->prev = tail;
            tail = tail->next;*/
            if (minVal > val)
                minVal = val;
            size++;
        }
    }
    void push_front(int val)
    {
        if (head == nullptr)
        {
            head = new DequeNode();
            head->Data = val;
            minVal = val;
            tail = head;
            size++;
        }
        else {
            head = head->CreatePrevNode(val);
            //head->prev = new DequeNode();
            //head->prev->Data = val;
            if (minVal > val)
                minVal = val;
            //head->prev->next = head;
            //head = head->prev;
            size++;
        }
    }
    int front()
    {
        if (head == nullptr)
        {
            return -1;
        }
        return head->Data;
    }
    int back() {
        if (tail == nullptr)
        {
            return -1;
        }
        return tail->Data;
    }
    void pop_front()
    {
        if (size == 0)
        {
            head = tail = nullptr;
            return;
        }
        if (head->next != nullptr)
        {
            DequeNode* node = head->next;
            delete head;
            head = node;
            head->prev = nullptr;
            size--;
        }
    }
    void pop_back()
    {
        if (size == 0)
        {
            head = tail = nullptr;
            return;
        }
        if (tail->prev != nullptr)
        {
            DequeNode* node = tail->prev;
            delete tail;
            tail = node;
            tail->next = nullptr;
            size--;
        }
    }
    //从头节点直接遍历到结尾节点
    int min_val() {
        int min_val = head->Data;
        DequeNode* node = head;
        while (node != nullptr)
        {
            if (min_val > node->Data)
            {
                min_val = node->Data;
            }
            node = node->next;
        }
        return min_val;
    }
    int Size() { return size; }
private:
    //这个是root节点
    DequeNode* head;//用于后向插入
    DequeNode* tail;    //用于前向插入
    int size;
    int minVal;
};
int maind()
{
    Deque s;
    /*s.push_back(5);
    s.push_back(6);
    s.push_back(7);
    s.push_back(3);
    s.push_back(1);*/

    s.push_front(1);
    s.push_front(3);
    s.push_front(7);
    s.push_front(6);
    s.push_front(5);
    printf("deque:front:%d,back:%d,min:%d", s.front(), s.back(), s.min_val());
    printf("size:%d\r\n", s.Size());
    // 5 6 7 3 1
    std::string line;
    cout << "0 popfront 1 popback 2 front 3 back 4 min" << endl;
    while (line != "exit")
    {
        cin >> line;
        //getline(cin, line);
        if (line == "0")
        {
            s.pop_front();
            printf("deque:front:%d,back:%d,min:%d", s.front(), s.back(), s.min_val());

        }
        if (line == "1")
        {
            s.pop_back();
            printf("deque:front:%d,back:%d,min:%d", s.front(), s.back(), s.min_val());
        }

    }

    return 0;
}