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Binary Tree Level Order Traversal II
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Binary Tree Level Order Traversal II
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/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public ArrayList<ArrayList<Integer>> levelOrderBottom(TreeNode root) {
// Note: The Solution object is instantiated only once and is reused by each test case.
ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
if(root == null) return result;
Stack<ArrayList<Integer>> container = new Stack<ArrayList<Integer>>();
Queue bfs = new LinkedList();
bfs.add(root);
helpler(bfs, container);
while(!container.isEmpty()){
result.add(container.pop());
}
return result;
}
private void helpler(Queue q, Stack<ArrayList<Integer>> s){
if(q.isEmpty()) return;
Queue replace = new LinkedList();
ArrayList<Integer> current = new ArrayList<Integer>();
while(!q.isEmpty()){
TreeNode child = (TreeNode)q.remove();
current.add(child.val);
if(child.left != null)
replace.add(child.left);
if(child.right != null)
replace.add(child.right);
}
s.push(current);
helpler(replace, s);
}
}