11614 - Etruscan Warriors Never Play Chess
Solution Description : Simple math problem n*(n+1)/2 = s n^2+n=2*s n^2+n+(-2*s)=0 Using quadratic equation ax^2+bx+c=0 del = sqrt(b*b-4*a*c) = sqrt(1-4*1*(-2s)) = sqrt(1+8s) we know x = (-b(+-) del)/2a Here i use only + value because del is always positive so n = (-1+sqrt(1+8s))/2 Input as double s then print n (where n is convert from double to long) |
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