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Choose n distinct number from n set
Suppose we have n set of numbers . we want to choose a number from each set that they were distinct . how we can do it efficiently ?
A -> 1 <= n <= 20 , 1 <= |s| <= 100 , 1 <= numbers <= 10^9
B -> 1 <= n <= 10^5 , 1 <= |s| <= 10^5 , 1 <= numbers <= 10^9
C -> In General ?
thanks in advance.
