[数据结构与算法]线性表：单链表

线性表特点：同一性，有穷性，有序性
线性表两种存储结构：顺序存储，链式存储
链式存储三种表：单链表，循环链表，双向链表
单链表基本运算：初始化，头插法建立，尾插法建立，按序号查找，按值查找，求长度，插入，删除，合并

//数据结构 第二章线性表 单链表
//2021.8.5
//by Walnut from NWU
#include<iostream>
#include<stack>
#include<cmath>
using namespace std;

typedef struct Node{
    int data;
    struct Node* next;
}Node,*LinkList;

void initList(LinkList* l) {//初始化为带头结点链表
    *l = (LinkList)malloc(sizeof(Node));
    (*l)->next = NULL;
}

void insertListTail(LinkList l,int n) {//尾插
    Node* p = l;
    while (p->next != NULL) {
        p = p->next;
    }
    Node* m = (Node*)malloc(sizeof(Node));
    m->data = n;
    p->next = m;
    m->next = NULL;
}

void insertListHead(LinkList l, int n) {//头插
    Node* p = l;
    Node* m = (Node*)malloc(sizeof(Node));
    m->data = n;
    m->next = l->next;
    p->next = m;
}

int listLength(LinkList l) {//获取长度
    int j = 0;
    Node* p = l;
    while (p->next != NULL) {
        p = p->next;
        j++;
    }
    return j;
}

int getListValue(LinkList l, int pos) {//获取指定位置元素
    Node* p = l;
    int j = 0;
    while (p->next != NULL) {
        j++;
        p = p->next;
        if (j == pos) {
            return p->data;
        }
    }
    return 0;
}

void insertListPos(LinkList l, int n, int pos) {//指定位置插入元素
    Node* p = l;
    int j = 0;
    while (p->next != NULL) {
        j++;
        p = p->next;
        if (j == pos - 1) {
            Node* m = (Node*)malloc(sizeof(Node));
            m->data = n;
            m->next = p->next;
            p->next = m;
        }
    }
}

int findListValue(LinkList l, int n) {//按值查找
    Node* p = l;
    int j = 0;
    while (p->next != NULL) {
        p = p->next;
        j++;
        if (p->data == n) {
            return j;
        }
    }
    return 0;
}

void delListAll(LinkList l) {//表清空
    Node* p = l;
    while (p->next != NULL) {
        Node* m = p;
        p = p->next;
        free(m);
    }
    l->next = NULL;
}

LinkList mergeList(LinkList l1, LinkList l2) {//合并两个有序链表
    LinkList l;
    initList(&l);
    Node* p = l;
    Node* t;
    Node* p1 = l1;
    Node* p2 = l2;
    while (p1->next != NULL && p2->next != NULL) {
        if (p1->next->data > p2->next->data) {//此处应画图理解
            t = p1; p1 = p2; p2 = t;
        }
        t = p1->next->next;
        p->next = p1->next;
        p = p->next;
        p1->next = t;
        t = p2->next->next;
        p->next = p2->next;
        p = p->next;
        p->next = NULL;
        p2->next = t;
    }
    if (p1->next != NULL) {
        p->next = p1->next;
    }
    if (p2->next != NULL) {
        p->next = p2->next;
    }
    return l;
}

void coutList(LinkList l) {//遍历输出
    if (l->next == NULL) {
        cout << "LIST EMPTY!" << endl;
        return;
    }
    Node* p = l;
    while (p->next != NULL) {
        p = p->next;
        cout << p->data << " ";
    }
    cout << "------LIST COUT DONE!" << endl;
}

void delListPos(LinkList l, int pos) {//删除指定位置元素
    Node* p = l;
    int j = 0;
    while (p->next != NULL) {
        if (j == pos - 1) {
            Node* m = p->next;
            p->next = m->next;
            free(m);
        }
        p = p->next;
        j++;

    }
}

int main() {
    LinkList l;//测试程序
    initList(&l);
    for (int i = 0; i < 5; i++) {
        insertListTail(l, i);
    }
    for (int i = 5; i < 10; i++) {
        insertListHead(l, i);
    }
    insertListPos(l, 15, 5);
    cout << "length: " << listLength(l) << endl;
    coutList(l);
    cout << "value[3]: " << getListValue(l, 3) << endl;
    cout << "pos of 3: " << findListValue(l, 3) << endl;
    cout << "delete pos 6,1" << endl;
    delListPos(l, 1);
    delListPos(l, 6);
    coutList(l);
    cout << "delete all" << endl;
    delListAll(l);
    coutList(l);

    LinkList l1, l2;
    initList(&l1);
    initList(&l2);
    insertListHead(l1, 4);
    insertListHead(l1, 2);
    insertListHead(l2, 3);
    insertListHead(l2, 1);
    insertListHead(l1, 0);
    cout << "l1: ";
    coutList(l1);
    cout << "l2: ";
    coutList(l2);
    LinkList l3 = mergeList(l1, l2);
    cout << "merge: ";
    coutList(l3);
    return 0;
}