题目

在二叉查找树中插入节点

给定一棵二叉查找树和一个新的树节点，将节点插入到树中。

你需要保证该树仍然是一棵二叉查找树。

样例

给出如下一棵二叉查找树，在插入节点6之后这棵二叉查找树可以是这样的：

  2             2
 / \           / 1   4   -->   1   4
   /             / \
  3             3   6

分析

递归和非递归两种方法实现。

Python代码

"""
Definition of TreeNode:
class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left, self.right = None, None
"""

class Solution:
    """
    @param root: The root of the binary search tree.
    @param node: insert this node into the binary search tree.
    @return: The root of the new binary search tree.
    """

    def insertNode1(self, root, node):
        # write your code here
        if root is None:
            root = node
            return root

        if node.val < root.val:
            root.left = self.insertNode1(root.left, node)
        else:
            root.right = self.insertNode1(root.left, node)

        return root

    def insertNode(self, root, node):
        # write your code here
        if root is None:
            root = node
            return root

        t = root
        while t is not None:
            if node.val < t.val:
                if t.left is None:
                    t.left = node
                    return root
                else:
                    t = t.left
                    continue
            else:
                if t.right is None:
                    t.right = node
                    return root
                else:
                    t = t.right
                    continue
        return root

GitHub -- Python代码

C++代码

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param root: The root of the binary search tree.
     * @param node: insert this node into the binary search tree
     * @return: The root of the new binary search tree.
     */
    TreeNode* insertNode1(TreeNode* root, TreeNode* node) {
        // write your code here
        if(root == NULL)
        {
            root = node;
            return root;
        }//if

        if(node->val < root->val)
        {
            if(root->left == NULL)
            {
                root->left = node;
            }else{
                root->left = insertNode1(root->left, node);
            }//else
        }else{
            if(root->right == NULL)
            {
                root->right = node;
            }else{
                root->right = insertNode1(root->right, node);
            }//else
        }//else

        return root;
    }

    //非递归
     TreeNode* insertNode(TreeNode* root, TreeNode* node) {
        // write your code here
        if(root == NULL)
        {
            root = node;
            return root;
        }//if

        TreeNode *t = root;
        while(t != NULL)
        {
            if(node->val < t->val)
            {

                if(t->left == NULL)
                {
                    t->left = node;
                    return root;
                }else{
                    t = t->left;;
                    continue;
                }//else
            }//if
            else{
                if(t->right == NULL)
                {
                    t->right = node;
                    return root;
                }else{
                    t = t->right;
                    continue;
                }//else
            }//else
        }//while
        return root;
     }
};

GitHub -- C++代码