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Create Day-26_Verify Preorder Serialization of a Binary Tree.py

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	`1`	`+class Solution(object):`
	`2`	`+ def isValidSerialization(self, preorder):`
	`3`	`+ """`
	`4`	`+ :type preorder: str`
	`5`	`+ :rtype: bool`
	`6`	`+ """`
	`7`	`+ # remember how many empty slots we have`
	`8`	`+ # non-null nodes occupy one slot but create two new slots`
	`9`	`+ # null nodes occupy one slot`
	`10`	`+`
	`11`	`+ p = preorder.split(',')`
	`12`	`+`
	`13`	`+ #initially we have one empty slot to put the root in it`
	`14`	`+ slot = 1`
	`15`	`+ for node in p:`
	`16`	`+`
	`17`	`+ # no empty slot to put the current node`
	`18`	`+ if slot == 0:`
	`19`	`+ return False`
	`20`	`+`
	`21`	`+ # a null node?`
	`22`	`+ if node == '#':`
	`23`	`+ # ocuppy slot`
	`24`	`+ slot -= 1`
	`25`	`+ else:`
	`26`	`+ # create new slot`
	`27`	`+ slot += 1`
	`28`	`+`
	`29`	`+ #we don't allow empty slots at the end`
	`30`	`+ return slot==0`

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