【LeetCode OJ】Populating Next Right Pointers in Each Node

Problem Link:

http://oj.leetcode.com/problems/populating-next-right-pointers-in-each-node/

Just traverse the tree from the root, level by level. Esay enough.

# Definition for a  binary tree node
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#         self.next = None

class Solution:
    # @param root, a tree node
    # @return nothing
    def connect(self, root):
        """
        We use a BFS from the root, so that we can traverse the tree level by level.
        We need two queues, to store the nodes of this level and next.
        """
        if root is None:
            return
        q = [root]
        while q:
            new_q = []
            for i in xrange(len(q)-1):
                q[i].next = q[i+1]
            q[-1].next = None
            for node in q:
                if node.left:
                    new_q.append(node.left)
                if node.right:
                    new_q.append(node.right)
            q = new_q