Solution.java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode insertIntoBST(TreeNode root, int val) {
            if (root == null) {
                return new TreeNode(val);
            }
            //指针
            TreeNode pos = root;
            //迭代
            while (pos != null) {
                if (val < pos.val) {
                    if (pos.left == null) {
                        pos.left = new TreeNode(val);
                        break;
                    } else {
                        pos = pos.left;
                    }
                } else {
                    if (pos.right == null) {
                        pos.right = new TreeNode(val);
                        break;
                    } else {
                        pos = pos.right;
                    }
                }
            }
            return root;
        }
    }