The building of a hacker rank is one that cost a lot of money and as such the minimum cost is 4.
The minimum cost is the lowest cost that is needed to complete a building. It depends on:
When one is given input such as : [[1,2,3],[1,2,3],[3,3,1]] (the values in column stands for the cost of materials)
The output : 4
So you have to:
Select material-1 of cost 1 in first house(row)
Select material-2 of cost 2 in second house(row)
Select material-3 of cost 1 in third house (row)
total = 1+2+1 -> 4
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