Java数据结构之二叉搜索树详解

public class TreeNode {
    public int val;
    public TreeNode left;
    public TreeNode right;

    public TreeNode() {
    }

    public TreeNode(int val) {
        this.val = val;
    }

    public TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

TreeNode head;
    private void init() {
        //添加一个头节点
        head = new TreeNode(-1);
    }

/**
     * 插入新节点，假设新节点均大于0
     * @param val 插入节点值
     * @return 插入的节点
     */
    public TreeNode insert(int val) {
        TreeNode temp = head;
        while (true) {
            if (temp.val < val) {
                //val应该在右子树上
                if (null != temp.right) {
                    temp = temp.right;
                    continue;
                } else {
                    temp.right = new TreeNode(val);
                    return temp.right;
                }
            }
            //应该在左子树上
            if (null != temp.left) {
                temp = temp.left;
                continue;
            }
            temp.left = new TreeNode(val);
            return temp.left;
        }
    }

/**
     * 搜索节点值
     * @param val
     * @return
     */
    public Pair<TreeNode, TreeNode> find(int val) {
        TreeNode temp = head.right;
        TreeNode parent = head;
        while (null != temp) {
            if (temp.val == val) {
                return Pair.of(temp, parent);
            }
            parent = temp;
            if (temp.val < val) {
                //在右子树上
                temp = temp.right;
                continue;
            }
            temp = temp.left;
        }
        return null;
    }

/**
     * 1.如果删除的是叶子节点直接删除，
     * 2.如果删除的节点只有左子树或者右子树，则直接将左子树或者右子树节点放在删除节点位置
     * 3.如果删除节点同时右左子树和右子树，则将右子树节点放在原来节点位置，将左子树放在右子树最左边节点左子树上
     * @param val
     */
    public void delete(int val) {
        //找到删除节点，删除节点父节点
        Pair<TreeNode, TreeNode> curAndParent = this.find(val);
        TreeNode cur = curAndParent.getLeft();
        TreeNode parent = curAndParent.getRight();
        //记录删除当前节点后，当前节点位置放置哪个节点
        TreeNode changed;
        if (null == cur.left && null == cur.right) {
            changed = null;
        } else if (null != cur.left && null != cur.right) {
            TreeNode tempRight = cur.right;
            while (null != tempRight.left) {
                //找到最左侧节点
                tempRight = tempRight.left;
            }
            tempRight.left = cur.left;
            changed = cur.right;
        } else if (null != cur.left) {
            changed = cur.left;
        } else {
            changed = cur.right;
        }
        if (parent.left == cur) {
            parent.left = changed;
            return;
        }
        parent.right = changed;
    }