Leetcode 114. Flatten Binary Tree to Linked List

1 classSolution {2  Public:3     voidFlatten (treenode*root) {4         if(!root)return;5Flatten (root->Left );6Flatten (root->Right );7         8treenode* right = root->Right ;9Root->right = root->Left ;TenRoot->left =NULL; One          while(root->Right ) { Aroot = root->Right ; -         } -Root->left =NULL; theRoot->right =Right ; -     } -};

Originally thought that the last flatten of the tree must be in order to small to large, so as to

3

1 4

2 5

The left side of the tree is 1-2-5, and the right side is flatten to insert the left subtree. Later found to think more, only need all the nodes have no left subtree, but still to follow a certain order.

Test instructions still very clear, leave the pit.

The order of the topics required is the pre-order, i.e. root-root->left-root->right.

Enter the tree above:

Your input

[3,1,4,2,5]

Your Answer

[3,null,1,null,2,null,5,null,4]

Expected answer

[3,null,1,null,2,null,5,null,4]   That is, indeed, the pre-order.


There are other algorithms, not seen, left pits.

Leetcode 114. Flatten Binary Tree to Linked List