In recurrence relation , floor , ceil , addition of constant terms etc are not required for solving as we need asymptotic solution..So
T(n) = T(n/2 - 1) + T(n - n/2) + θ(n)
==> T(n) = T(n/2) + T(n/2) + θ(n)
==> T(n) = 2T(n/2) + θ(n)
==> T(n) = θ(nlogn) [Using 3rd case of Master's Theorem]