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Copy pathBinaryTreeLevelOrderTraversalII.java
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47 lines (37 loc) · 1.36 KB
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Copy pathBinaryTreeLevelOrderTraversalII.java
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47 lines (37 loc) · 1.36 KB
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/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<List<Integer>> levelOrderBottom(TreeNode root) {
List<List<Integer>> result = new ArrayList<List<Integer>>();
if (root == null) return result;
Queue<TreeNode> q1 = new LinkedList<TreeNode>();
Queue<TreeNode> q2 = new LinkedList<TreeNode>();
List<Integer> level = new ArrayList<Integer>();
q1.add(root);
while (!q1.isEmpty()) {
TreeNode node = q1.remove();
level.add(node.val);
if (node.left != null) q2.add(node.left);
if (node.right != null) q2.add(node.right);
if (q1.isEmpty()) {
result.add(level);
level = new ArrayList<Integer>();
Queue<TreeNode> temp = q1;
q1 = q2;
q2 = temp;
}
}
List<List<Integer>> reversed_result = new ArrayList<List<Integer>>();
for (int i = result.size() - 1; i >= 0; i--) {
reversed_result.add(result.get(i));
}
return reversed_result;
}
}