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Copy pathFlatternBinaryTreeToLinkedList.java
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Copy pathFlatternBinaryTreeToLinkedList.java
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70 lines (66 loc) · 1.42 KB
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/*
Given a binary tree, flatten it to a linked list in-place.
For example,
Given
1
/ \
2 5
/ \ \
3 4 6
The flattened tree should look like:
1
\
2
\
3
\
4
\
5
\
6
*/
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
// Recursion
public class Solution {
public TreeNode flatten(TreeNode root) {
if (root == null) return root;
TreeNode r = root.right;
if (root.left != null) {
root.right = root.left;
root.left = null;
root = flatten(root.right);
}
if (r != null) {
root.right = r;
root = flatten(root.right);
}
return root;
}
}
// Preorder traversal
public class Solution {
TreeNode prev;
public TreeNode flatten(TreeNode root) {
flat(root);
return root;
}
public void flat(TreeNode root){
if (root == null) return;
TreeNode l = root.left, r = root.right;
if (prev != null) prev.right = root;
root.left = null;
root.right = null;
prev = root;
flat(l);
flat(r);
}
}