Convert Binary Tree to Linked Lists by Depth
http://lintcode.com/en/problem/convert-binary-tree-to-linked-lists-by-depth/
/**
* Definition of TreeNode:
* public class TreeNode {
* public int val;
* public TreeNode left, right;
* public TreeNode(int val) {
* this.val = val;
* this.left = this.right = null;
* }
* }
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
/**
* @param root the root of binary tree
* @return a lists of linked list
*/
public List<ListNode> binaryTreeToLists(TreeNode root) {
// Write your code here
List<ListNode> result = new ArrayList<ListNode>();
dfs(root, 1, result);
return result;
}
void dfs(TreeNode root, int depth, List<ListNode> result) {
if(root == null){
return;
}
ListNode node = new ListNode(root.val);
if(result.size() < depth){
result.add(node);
}else{
node.next = result.get(depth - 1);
result.set(depth - 1, node);
}
dfs(root.right, depth + 1, result);
dfs(root.left, depth + 1, result);
}
}