Insert node to BST

  • 难度:简单

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

挑战

能否不使用递归?

Solution

简单题,每个node决定是往左还是往右还是就是这个节点。类似二分的做法。

Code

/**
 * 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) {
        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;
    }
}