117. Populating Next Right Pointers in Each Node II

Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.

Initially, all next pointers are set to NULL.






def connect(root: 'Node'):   
    cur = root, left_most = None prev = None
   
    while cur:
        if cur.left:
            if prev:
                prev.next = cur.left
            else:
                left_most = cur.left
            prev = cur.left
        if cur.right:
            if prev:
                prev.next = cur.right
            else:
                left_most = cur.right
            prev = cur.right
       
        if cur.next:
            cur = cur.next
        else:
            cur = left_most
            prev = None
            left_most = None       
    return root
 

def connect(root: 'Node'):
   
    if not root:
        return root
    q = deque()
    q.append((root,0))
   
    levels = {}
    while q:
        cur, level = q.popleft()
       
        if level not in levels:
            levels[level] = []
       
        levels[level].append(cur)
       
        if cur.left:
            q.append((cur.left, level+1))
        if cur.right:
            q.append((cur.right, level+1))
                       
   
    for level in levels:
        for i in range(len(levels[level])-1):
            levels[level][i].next = levels[level][i+1]
           
    return root

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