题解 | #二叉搜索树的第k个节点#
二叉搜索树的第k个节点
http://www.nowcoder.com/practice/57aa0bab91884a10b5136ca2c087f8ff
import java.util.; import java.util.ArrayList; /
- public class TreeNode {
- int val = 0;
- TreeNode left = null;
- TreeNode right = null;
- public TreeNode(int val) {
-
this.val = val; - }
- } */
public class Solution { /** * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可 * * * @param proot TreeNode类 * @param k int整型 * @return int整型 */ public int KthNode (TreeNode proot, int k) { if(proot==null){ return -1; } ArrayList nodelist=getNum(proot); if(nodelist.size()<k||k==0){ return -1; } Collections.sort(nodelist); return Integer.valueOf(nodelist.get(k-1)); } public ArrayList getNum (TreeNode proot ) { ArrayList list=new ArrayList(); if(proot!=null){ list.add(proot.val); }else{ return null; } if(proot.left!=null){ list.addAll(getNum(proot.left)); } if(proot.right!=null){ list.addAll(getNum(proot.right)); } return list; } }
