DefaultDict Tutorial

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    print(' '.join(map(str,** d[input()]**)) or -1)

    Can you explain me how it works--> ("d[input()")

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      so first in for loop range(n), it gets all the index of a and b, which is [1,2,4], [3,5] then in for loop range(m) it checks: where is a's index ? where is b's index if a's index or b's index == None, that means d[input()] in for loop range(m) == [] right?(it's None). So in this python doc:https://docs.python.org/3/library/stdtypes.html#truth-value-testing it shows that: "empty sequences and collections: '', (), [], {}, set(), range(0)" are considered False. So if it False, with False and -1, it's a boolean operator, simple, right ? It prints -1. Hope u can understand

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      if we don't want to store the input() value then we can do like this. Here input() will execute and asks for users input() and then it will check the particular key in defaultdict and return a list.So know we wanna concatenate the list values but .join() always receives string instance so we need to type cast each element of returned list into string so we are using map function. map() will retrieve element of list one by one and type cast it to string...