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[LeetCode]102 Binary Tree Level Order Traversal
https://oj.leetcode.com/problems/binary-tree-level-order-traversal/
http://blog.csdn.net/linhuanmars/article/details/23404111
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<List<Integer>> levelOrder(TreeNode root) {
// This is how we use queue to iterate a tree.
// To let nodes on the same level be returned in the same list, we can store an extra level for each nodes.
List<List<Integer>> result = new ArrayList<>();
if (root == null)
return result;
Queue<NodeWithLevel> queue = new LinkedList<>();
queue.offer(new NodeWithLevel(root, 0));
while (!queue.isEmpty())
{
NodeWithLevel nodeWithLevel = queue.poll();
if (nodeWithLevel.level == result.size())
result.add(new ArrayList<Integer>());
result.get(nodeWithLevel.level).add(nodeWithLevel.node.val);
if (nodeWithLevel.node.left != null)
{
queue.offer(new NodeWithLevel(nodeWithLevel.node.left, nodeWithLevel.level + 1));
}
if (nodeWithLevel.node.right != null)
{
queue.offer(new NodeWithLevel(nodeWithLevel.node.right, nodeWithLevel.level + 1));
}
}
return result;
}
private static class NodeWithLevel
{
TreeNode node;
int level;
NodeWithLevel(TreeNode node, int level)
{
this.node = node;
this.level = level;
}
}
}[LeetCode]102 Binary Tree Level Order Traversal
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