2.3 链表与邻接链表

　　数组是一种支持随机访问的数据结构，而链表支持在结构中间某个位置插入和删除数据的时间复杂度$O(1)$的数据结构。

struct Node{
    int v;
    struct Node *p, *n;

    Node(int val): v(val) {}
};

Node* head, * tail;

void initialize(){
    head = new Node();
    tail = new Node();
    head->n = tail;
    tail->p = head;
}

void insert(Node* p, int val){
    Node* t = new Node(val);

    t->n = p->n;
    p->n->p = t;
    p->n = t;
    t->p = p;
}

void remove(Node* p){
    p->n->p = p->p;
    p->p->n = p->n;
    delete p;
}

void free_node(){
    Node* t;
    while(head){
        t = head->n;
        delete head;
        head = t;
    }
}

1. 邻接表

const int N = BUFSIZE;
int idx = 1;
int h[N], e[N], ne[N], w[N];
void add(int a, int b, int c){
    e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++; 
}

void visit(int x){
    for(int i = h[x]; i; i = ne[i]){
        int j = e[i];
        // todo:
    }
}

　　

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