The number of operations of Explicit and Implicit Euler for 1D hear equation
Note that

$U^n_j + \mu (U^n_{j+1}-2U^n_j+U^n_{j-1}) = (1-2\mu)U^n_j+\mu(U^n_{j+1}+U^n_{j-1})$

$1-2\mu$ may be precomputed.