May LeetCoding Challenge20 之 二叉树中序遍历

因为题目为二叉搜索树找到第k大的数，所以对二叉搜索树中序遍历一定是有序的。

分为两种：递归 和 迭代(栈)

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 LinkedList<Integer> inorder(TreeNode root, LinkedList<Integer> arr){
        if(root == null) return arr;
        inorder(root.left, arr);
        arr.add(root.val);
        inorder(root.right, arr);
        return arr;
    }
    public int kthSmallest(TreeNode root, int k) {
        LinkedList<Integer> nums = inorder(root, new LinkedList<>());
        return nums.get(k-1);
    }
}

标签：LeetCoding,right,TreeNode,val,May,arr,int,二叉树,root
来源： https://www.cnblogs.com/yawenw/p/12944367.html