Hashmap implementation issue

#1

in the video,it is given that we can optimize by making a different hash map as soon as we get to a new common prefix but the complexity of this structure is not good.please tell how to implement this kind of structure
in which we create a different hash map as soon as we get a new common prefix.i am not able to get it on my own

#2

@Rj.25
At which point was it mentioned
Please mentiion that

#3

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