題目

給定一棵二叉查找樹和一個新的樹節(jié)點，將節(jié)點插入到樹中。
你需要保證該樹仍然是一棵二叉查找樹。

分析

分別用遞歸和非遞歸兩種方法實現。本質上會發(fā)現，兩種方法類似

public 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.
     */
    public TreeNode insertNode(TreeNode root, TreeNode node) {
        if(root == null)
            return node;
            
        if(root.val > node.val)
            root.left = insertNode(root.left, node);
        else
            root.right = insertNode(root.right, node);
        
        return root;
    }
}

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public 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.
     */
    public TreeNode insertNode(TreeNode root, TreeNode node) {
        // write your code here
        if (root == null) {
            root = node;
            return root;
        }
        TreeNode tmp = root;
        TreeNode last = null;
        while (tmp != null) {
            last = tmp;
            if (tmp.val > node.val) {
                tmp = tmp.left;
            } else {
                tmp = tmp.right;
            }
        }
        if (last != null) {
            if (last.val > node.val) {
                last.left = node;
            } else {
                last.right = node;
            }
        }
        return root; 
    }
}