一 非递归方式
/*
public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;
public TreeNode(int val) {
this.val = val;
}
}
*/
import java.util.Stack;
public class Solution {
TreeNode KthNode(TreeNode pRoot, int k)
{
if(pRoot == null || k <= 0){
return null;
}
Stack<TreeNode> stack = new Stack<TreeNode>();
int index = 0;
while(pRoot != null || !stack.isEmpty()){
if(pRoot != null){
stack.push(pRoot);
pRoot = pRoot.left;
}else{
pRoot = stack.pop();
index++;
if(index == k){
return pRoot;
}
pRoot = pRoot.right;
}
}
return null;
}
}
二 递归方式
/*
public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;
public TreeNode(int val) {
this.val = val;
}
}
*/
public class Solution {
int index = 0;
TreeNode KthNode(TreeNode root, int k)
{
if(root != null){
TreeNode node = KthNode(root.left, k);//左边遍历
if(node != null){
return node;
}
index++;
if(index == k){
return root;
}
node = KthNode(root.right, k);//右边遍历
if(node != null){
return node;
}
}
return null;
}
}