Editorial for GlobeX Cup '18 S1 - Code Copiers


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Submitting an official solution before solving the problem yourself is a bannable offence.

Author: Ninjaclasher

We can use a boolean array k to store whether there is a coder who this coder copies from. An element i in the array is True if coder i is not a source.

For all i, we set k_{a_i} = True, meaning that coder a_i is not a source.

Then, we can loop through the boolean array and count the number of False elements.

Time Complexity: \mathcal{O}(N)


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