红黑树 (洛谷 P3369 【模板】普通平衡树 )

(以前学习的红黑树，在今天写算法大作业的时候用到了，哈哈， 即使研究生也要继续学习算法呀）

红黑树的五条性质:

  1) 节点颜色为红色或黑色

  2) 根节点为黑色

  3) 每一个叶子节点两个NIL节点也为黑色

  4) 红色节点后继为黑色

  5) 从根节点到叶子节点简单路径黑高相同

红黑树是一颗自平衡的二叉查找树, 查询,插入,删除的时间复杂度都为O(logn)

红黑树简直就是一棵神奇的数据结构~~~~~~~~,我很想知道他们的灵感从哪里来的. 据说红黑树是2-3树的变形, RNtree的插入操作类比2-3树我还可以理解.

但BRtree那个删除操作真的好简洁于奇妙~~向这些科学家致敬!!

 总结一下:

       (1)  插入节点z默认时红色,   可能违反的性质:
            1)  z的parent节点颜色是红色
            2)  根节点是红色

     插入时关键要看叔叔节点

     (2)  删除节点y,并且用x节点代替,可能违反的性质

           1)  经过x的路径,黑高减1
           2) x的为红色,x的parent也是红
           3) x为根节点,颜色为红色

    删除时要看兄弟节点

代码的逻辑时根据算法导论的逻辑写出, 并且经过洛谷P3369习题验证

(这是我提交过的最长代码.....

#include <bits/stdc++.h>
using namespace std;
#define RED 1
#define BLACK 0
#define RBnode node<T> *

template <class T>
struct node {
    T key;
    int sum; //sum子树节点数
    bool color;
    node *p, *left, *right;
    node() {
        sum = 0; color = BLACK;
    }
    node(T key, int sum, int color, node *p, node *left, node *right) :
        key(key), sum(sum), color(color), p(p), left(left), right(right) {}
    void up() {
        sum = 1 + left->sum + right->sum; // nil节点不更新
    }
};

template <class T>
class  RBtree {
private:
    RBnode rt;
    RBnode nil;
public:
    RBtree() {
        nil = new node<T>();
        nil->p = nil->left = nil->right = nil;
        rt = nil;
    }

    void mid_print(RBnode x) { // 中序遍历
        if (x == nil) return;
        mid_print(x->left);
        cout << "key: " << x->key << " color:" << x->color << " sum: " << x->sum << endl;
        mid_print(x->right);
    }

    void  my_print() {
        mid_print(rt);
    }

    void insert(T key) {
        RBnode z = new node<T>(key, 1, RED, nil, nil, nil);
        RBnode y = nil; // y: x的parent;
        RBnode x = rt;
        while (x != nil) {
            y = x;
            if (z->key <= x->key)
                x = x->left;
            else
                x = x->right;
        }
        z->p = y;  // 特别的根节点父节点是nil
        if (y == nil)
            rt = z;
        else if (z->key <= y->key)
            y->left = z;
        else
            y->right = z;
        // sum的改变
        while (y != nil) {
            y->up();
            y = y->p;
        }
        insert_fixup(z);
    }

    // 可能违反的性质:
    // 1)z的parent节点颜色是红色
    // 2)根节点是红色 
    void insert_fixup(RBnode z) {  // 插入看叔叔节点 
        while (z->p->color == RED) {
            if (z->p == z->p->p->left) {
                RBnode uncle = z->p->p->right;
                if (uncle->color == RED) { // case1 叔叔节点是红色; 叔叔和父亲加一层黑色,祖父层变黑(黑色上移)
                    z->p->color = BLACK;
                    uncle->color = BLACK;
                    z->p->p->color = RED;
                    z = z->p->p;
                }
                else {
                    if (z->p->right == z) { // case2 叔叔是黑色, 祖孙三代不在一条直线, 调整到case3 
                        z = z->p;
                        left_rotate(z);
                    }
                    z->p->color = BLACK;  // case3 调整过后,冲突解决
                    z->p->p->color = RED;
                    right_rotate(z->p->p);
                }
            }
            else {
                RBnode uncle = z->p->p->left;
                if (uncle->color == RED) { // case1
                    z->p->color = BLACK;
                    uncle->color = BLACK;
                    z->p->p->color = RED;
                    z=z->p->p;
                }
                else {
                    if (z->p->left == z) { // case 2
                        z = z->p;
                        right_rotate(z);
                    }
                    z->p->color = BLACK;  // case 3
                    z->p->p->color = RED;
                    left_rotate(z->p->p);
                }
            }
        }
        rt->color = BLACK;
    }

    // 旋转的性质: 左旋或右旋后,交换两节点的颜色不改变黑高(自我总结)
    void left_rotate(RBnode x) {
        RBnode y = x->right;
        x->right = y->left;
        if (y->left != nil)
            y->left->p = x;
        y->p = x->p;
        if (x->p == nil)
            rt = y;
        else if (x->p->left == x)
            x->p->left = y;
        else
            x->p->right = y;
        y->left = x;
        x->p = y;
        if (x!=nil) x->up(); // 先调整x,再调整y
        if (y!=nil) y->up();
    }

    void right_rotate(RBnode x) {
        RBnode y = x->left;
        x->left = y->right;
        y->p = x->p;
        if (y->right != nil)
            y->right->p = x;
        if (x->p == nil)
            rt = y;
        else if (x->p->left == x)
            x->p->left = y;
        else
            x->p->right = y;
        y->right = x;
        x->p = y;
        if (x!=nil) x->up();
        if (x!=nil) y->up();
    }

    RBnode min_mum(RBnode x) {
        while (x->left != nil)
            x = x->left;
        return x;
    }

    RBnode max_mum(RBnode x) {
        while (x->right != nil)
            x = x->right;
        return x;
    }

    RBnode low_find(int k) { // 寻找比k小且最大的节点
        return _low(k,rt);
    }

    RBnode _low (int k, RBnode x) {
        if (x==nil) return x;
        if (k<=x->key) return _low(k,x->left);
        else {
            RBnode ans=_low(k,x->right);
            if (ans!=nil) return ans;
            else          return x;
        }
    }

    RBnode upp_find(T k) { // 寻找比k大且最小的节点
        return _upp(k,rt);
    }

    RBnode _upp (T k, RBnode x) {
        if (x==nil) return x;
        if (k>=x->key) return _upp(k,x->right);
        else {
            RBnode ans=_upp(k,x->left);
            if (ans!=nil) return ans;
            else          return x;
        }
    }

    RBnode rfind(T key) {  // 相等元素的最后一个节点
        RBnode x = rt;
        while (x != nil) {
            if (key<x->key)
                x = x->left;
            else if (key>x->key)
                x = x->right;
            else
                return x;
        }
        return x;
    }

    RBnode find(T key) {  // 相等元素第一个节点
        return my_find(key, rt);
    }

    RBnode my_find(T key, RBnode x) {
        if (x == nil) return nil;
        if (key<x->key) return my_find(key, x->left);
        if (key == x->key) {
            RBnode ans = my_find(key, x->left);
            if (ans == nil) return x;
            else          return ans;
        }
        return my_find(key, x->right);
    }

    RBnode find_kth(int k) {  // 排名第k的元素, 相等的元素具有不同的排名
        RBnode x = rt;
        if (rt->sum<k) return nil;
        while (k != x->left->sum + 1) {
            if (k <= x->left->sum)
                x = x->left;
            else {
                k -= x->left->sum + 1;
                x = x->right;
            }
        }
        return x;
    }

    int get_rank(RBnode x) { // 寻找节点x的排名
        RBnode t=rt; int k=0;
        while (t!=x) {
            if (x->key<=t->key)
                t=t->left;
            else  {
                k+=t->left->sum+1;
                t=t->right;                
            }
        }
        return k+t->left->sum+1;
    }

    void transplate(RBnode y, RBnode x) {  // 以节点x代替y,但不对y的子节点经行替换
        if (y->p == nil)
            rt = x;
        else if (y->p->left == y)
            y->p->left = x;
        else
            y->p->right = x;
        x->p = y->p;
    }

    void remove(RBnode z) {  // y: 要删除的节点  x: 代替的节点
        RBnode y = z;
        RBnode x;
        int ycolor = y->color;
        if (y->left == nil) {
            x = y->right;
            transplate(y, x);
        }
        else if (y->right == nil) {
            x = y->left;
            transplate(y, x);
        }
        else {
            y = min_mum(y->right);
            ycolor = y->color;
            x = y->right;
            if (y->p == z)
                x->p = y;  // x可能是nil节点,因此需要记录其父亲
            else {
                transplate(y, x);
                y->right = z->right;
                z->right->p = y;
            }
            transplate(z,y);
            y->left = z->left;
            z->left->p = y;
            y->color = z->color; // y代替z,但颜色不改变!!!!!!
            y = z;  // y指向废弃节点
        }
        if (ycolor == BLACK)
            remove_fixup(x);
        RBnode t=x->p; // 最后调整sum
        while (t!=nil) { 
            t->up();
            t=t->p;
        }
        delete y;
    }

    // 可能有冲突:
    // 1)经过x的路径,黑高减1
    // 2)x的为红色,x的parent也是红
    // 3)x为根节点,颜色为红色
    void remove_fixup(RBnode x) { // 看兄弟节点 // 减少x多的一重黑色
        while (x != rt&&x->color == BLACK) {
            if (x == x->p->left) {
                RBnode bro = x->p->right;
                if (bro->color == RED) { // case1 兄弟节点为红色,转化为情况234 
                    bro->color = BLACK;
                    bro->p->color = RED;
                    left_rotate(x->p);
                    bro = x->p->right;
                }
                if (bro->left->color == BLACK&&bro->right->color == BLACK) { // case2 兄弟节点及其儿子节点都为黑色
                    bro->color = RED;
                    x = x->p;
                }
                else {
                    if (bro->right->color == BLACK) { // case3 兄弟右节点不为红色
                        bro->color = RED;
                        bro->left->color = BLACK;
                        right_rotate(bro);
                        bro = x->p->right;
                    }
                    bro->right->color = BLACK; //case4   兄弟右孩子节点为红色,调整之后结束循环
                    bro->color = bro->p->color;
                    bro->p->color = BLACK;
                    left_rotate(x->p);
                    x = rt; // 终止递归
                }
            }
            else {
                RBnode bro = x->p->left;
                if (bro->color == RED) { // case 1
                    bro->color = BLACK;
                    bro->p->color = RED;
                    right_rotate(x->p);
                    bro = x->p->left;
                }
                if (bro->left->color == BLACK&&bro->right->color == BLACK) { // case 2
                    bro->color = RED;
                    x = x->p;
                }
                else {
                    if (bro->left->color == BLACK) { // case 3
                        bro->color = RED;
                        bro->right->color = BLACK;
                        left_rotate(bro);
                        bro = x->p->left;
                    }
                    bro->left->color = BLACK; // case 4
                    bro->color = bro->p->color;
                    bro->p->color = BLACK;
                    right_rotate(x->p);
                    x = rt;
                }
            }
        }
        x->color = BLACK;
    }

     RBnode successor(RBnode x) { // 后继节点
        if (x->right != nil)
            return min_mum(x->right);
        RBnode y = x->p;
        while (y != nil && y->right == x) {
            x = y;
            y = y->p;
        }
        return y;
    }

    RBnode predecessor(RBnode x) { // 前继
        if (x->left != nil)
            return max_mum(x->left);
        RBnode y = x->p;
        while (y != nil && y->left == x) {
            x = y;
            y = y->p;
        }
        return y;
    }

};

int main()
{

    RBtree<int> tree;
    int n;  scanf("%d",&n);
    while (n--) {
        int op,x; scanf("%d %d",&op,&x);
        if (op==1) tree.insert(x);
        else if(op==2)  {
            node<int>* nd=tree.rfind(x);
            tree.remove(nd);
        }
        else if(op==3) {
            node<int>* nd=tree.find(x);
            printf("%d\n",tree.get_rank(nd));
        }
        else if (op==4)  printf("%d\n",tree.find_kth(x)->key);
        else if (op==5)  printf("%d\n",tree.low_find(x)->key);
        else             printf("%d\n",tree.upp_find(x)->key);
    }
    return 0;
}