题解 | #二叉搜索树与双向链表#

开辟一个数组存储节点然后依次向下指但是空间复杂度为O（n），不满足题意、。。。。。。

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
import java.util.*;
public class Solution {
    ArrayList<TreeNode> we = new ArrayList<>();
    public TreeNode Convert(TreeNode pRootOfTree) {
        deep(pRootOfTree);
        System.out.print(we.size());
        if(pRootOfTree == null || (pRootOfTree.left == null && pRootOfTree.right == null)){
            return pRootOfTree;
        }
        for(int i=0;i<we.size();i++){
            if(i == 0){
                we.get(i).left = null;
                we.get(i).right = we.get(i+1);
            }
            else if(i == we.size() - 1){
                we.get(i).left = we.get(i-1);
                we.get(i).right = null;
            }
            else{
                we.get(i).left = we.get(i-1);
                we.get(i).right = we.get(i+1);
            }
            
        }
        
        return we.get(0);
    }
    public TreeNode deep(TreeNode pRootOfTree){
        if(pRootOfTree == null){
            return null;
        }
        deep(pRootOfTree.left);
        we.add(pRootOfTree);
        deep(pRootOfTree.right);
        return null;
    }
}