To prove safety: binary search trees and doubly-linked list

Title Description

Enter a binary search tree, the binary search tree converted into a doubly linked list sorted. Requirements can not create any new node, point to only adjust the tree node pointer.

 

examples:

 

solution:

Because it is a binary search tree, so in order to traverse the result is sorted.

Inorder traversal achieved by using a stack. When traversing, right after a point before a junction node, a rear left node point before a junction point. (10 connects the left subtree of the maximum value, the minimum simultaneous connections right subtree.)

 

public TreeNode convert(TreeNode root){
       if(root==null){
           return null;
       }
       Stack<TreeNode> stack = new Stack<>();
       TreeNode cur = root;
       TreeNode res = null;
       TreeNode pre = null;
       while(cur != null || !stack.isEmpty()){
           if(cur != null){
               stack.push(cur);
               cur = cur.left;
           }else{
               cur = stack.pop();
               if(pre == null){
                   pre = cur;
                   res = pre;
               }else{
                   pre.right = cur;
                   cur.left = pre;
                   pre = cur;
               }
               cur = cur.right;
           }
      }
     return res;
}

 

It can be converted to recursively