for i = 1 to n
ans+=pow(x,i)
can it calculated in less than o(n) ? thanks in advance
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Also you can do it preety easily in .
This is the sum of a geometric series so it can be calculated fast by divide and conqueror approach.
Let n = 2k then y = x1 + x2 + ... + xk, and then the sum is y + xk * y.