  Measurements of the effective lifetimes in the $B_{s}^{0} \rightarrow
K^{+}K^{-}$, $B^{0} \rightarrow K^{+}\pi^{-}$ and $B_{s}^{0} \rightarrow
\pi^{+}K^{-}$ decays are presented using $1.0~\mathrm{fb^{-1}}$ of $pp$
collision data collected at a centre-of-mass energy of 7 TeV by the LHCb
experiment. The analysis uses a data-driven approach to correct for the decay
time acceptance. The measured effective lifetimes are
  $\tau_{B_{s}^{0} \rightarrow K^{+}K^{-}}$ =
$1.407~\pm~0.016~\pm~0.007~\mathrm{ps}$,
  $\tau_{B^{0} \rightarrow K^{+}\pi^{-}}$ =
$1.524~\pm~0.011~\pm~0.004~\mathrm{ps}$,
  $\tau_{B_{s}^{0} \rightarrow \pi^{+}K^{-}}$ =
$1.60~\pm~0.06~\pm~0.01~\mathrm{ps}$.
  This is the most precise determination to date of the effective lifetime in
the $B_{s}^{0} \rightarrow K^{+}K^{-}$ decay and provides constraints on
contributions from physics beyond the Standard Model to the $B_{s}^{0}$ mixing
phase and the width difference $\Delta\Gamma_{s}$.
