红黑树的操作（二）

红黑树的节点删除：

1、如果删除的节点的孩子节点补上来是红色的，就直接将孩子涂成黑色；

2、删除节点没有红色的孩子节点时的情况

A:兄弟节点是黑色的，而且兄弟的孩子节点都是黑色的.

C.color = Color.RED;

X = A;

B:兄弟节点是黑色的，兄弟节点的孩子节点是左黑右红

A.color =  C.color;

C.color = A.color;

E.color = Color.BLACK;

leftRotate(C);

 

C:兄弟节点是黑色的，兄弟节点的孩子节点是左红右黑

C.color = A.color;

A.color = Color.RED;

E.color = Color.RED;

leftRotate(C);

D：兄弟节点是黑色的，兄弟节点的孩子节点是左红右黑

C.color = D.color;

D.color = C.color;

rightRotate(C);

E：兄弟节点是红色的

C.color  = A.color;

A.color = C.color;

lefRotate(A);

 

删除的代码示例：

/**
     * 红黑树删除节点
     * @param data
     */
    public void remove(T data){
        if(this.root == null)
            return;

        RBNode<T> cur = this.root;
        while(cur != null){
            if(cur.getData().compareTo(data) > 0){
                cur = cur.getLeft();
            } else if(cur.getData().compareTo(data) < 0){
                cur = cur.getRight();
            } else {
                break;
            }
        }

        if(cur == null){
            return;
        }

        if(cur.getLeft() != null && cur.getRight() != null){
            RBNode<T> old = cur;
            cur = cur.getLeft();
            while(cur.getRight() != null){
                cur = cur.getRight();
            }
            old.setData(cur.getData());
        }

        // 删除cur指向的节点
        RBNode<T> child = cur.getLeft();
        if(child == null){
            child = cur.getRight();
        }

        if(child != null){
            child.setParent(cur.getParent());
            if(cur.getParent() == null){
                this.root = child;
            } else {
                if(cur.getParent().getLeft() == cur){
                    cur.getParent().setLeft(child);
                } else {
                    cur.getParent().setRight(child);
                }
            }

            if(color(cur) == Color.BLACK){
                fixAfterRemove(child);
            }
        } else {
            if(cur.getParent() == null){
                this.root = null;
            } else {
                if(color(cur) == Color.BLACK){
                    fixAfterRemove(cur);
                }

                if(cur.getParent().getLeft() == cur){
                    cur.getParent().setLeft(null);
                } else {
                    cur.getParent().setRight(null);
                }
            }
        }
    }
    private void fixAfterRemove(RBNode<T> node) {
        while(color(node) == Color.BLACK){
            if(node == left(parent(node))){
                // 左子树删除黑色节点
                RBNode<T> brother = right(parent(node));
                if(color(brother) == Color.RED){ // 情况4
                    setColor(brother, Color.BLACK);
                    setColor(parent(node), Color.RED);
                    leftRotate(parent(node));
                    brother = right(parent(node));
                }

                if(color(left(brother)) == Color.BLACK // 情况1
                        && color(right(brother)) == Color.BLACK){
                    setColor(brother, Color.RED);
                    node = parent(node);
                } else {
                    // 情况3的前半段
                    if(color(right(brother)) != Color.RED){
                        setColor(brother, Color.RED);
                        setColor(left(brother), Color.BLACK);
                        rightRotate(brother);
                        brother = right(parent(node));
                    }

                    // 统一处理情况2
                    setColor(brother, color(parent(node)));
                    setColor(parent(node), Color.BLACK);
                    setColor(right(brother), Color.BLACK);
                    leftRotate(parent(node));
                    break;
                }
            } else {
                // 右子树删除黑色节点
                RBNode<T> brother = left(parent(node));
                if(color(brother) == Color.RED){ // 情况4
                    setColor(brother, Color.BLACK);
                    setColor(parent(node), Color.RED);
                    rightRotate(parent(node));
                    brother = left(parent(node));
                }

                if(color(left(brother)) == Color.BLACK // 情况1
                        && color(right(brother)) == Color.BLACK){
                    setColor(brother, Color.RED);
                    node = parent(node);
                } else {
                    // 情况3的前半段
                    if(color(left(brother)) != Color.RED){
                        setColor(brother, Color.RED);
                        setColor(right(brother), Color.BLACK);
                        leftRotate(brother);
                        brother = left(parent(node));
                    }

                    // 统一处理情况2
                    setColor(brother, color(parent(node)));
                    setColor(parent(node), Color.BLACK);
                    setColor(left(brother), Color.BLACK);
                    rightRotate(parent(node));
                    break;
                }
            }
        }
        // 在当前这一路遇见红色节点，直接补一个黑色节点
        setColor(node, Color.BLACK);
    }