0897.increasing-order-search-tree

897. Increasing Order Search Tree

题目

Given a tree, rearrange the tree in in-order so that the leftmost node in the tree is now the root of the tree, and every node has no left child and only 1 right child.

Example 1:
Input: [5,3,6,2,4,null,8,1,null,null,null,7,9]

       5
      / \
    3    6
   / \    \
  2   4    8
 /        / \
1        7   9

Output: [1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]

1
 \
  2
   \
    3
     \
      4
       \
        5
         \
          6
           \
            7
             \
              8
               \
                 9

Note:

• The number of nodes in the given tree will be between 1 and 100.
• Each node will have a unique integer value from 0 to 1000.

解题思路

见程序注释