Algorithm 3 Failure recovery algorithm.

Input: physical WSN $G^S$; VSNR $G_T^V$; node mapping results set $NODE=\{n_j^s,\cdots ,n_k^s\}$; Fault physical sensor node $n_x^s$ Output: Failure recovery result $RM=\{n_1^s,\cdots n_m^s\}$ Initialization: Failure recovery result $RM=\varnothing$ if$n_x^s$ fault then       Rank invalid m VSNs in descending order by penalty end if for$i=1,\cdots ,m$do           $G^S\leftarrow G^S/\{n_x^s,l_{xi}^s,l_{ix}^s\}$           for $n_i^v$ in VSNi do              if $n_i^v$ is critical virtual sensor node then                Remap $n_j^v$ to $n_i^s$ through formula (24)                Add $n_i^s$ to $RM$           else             find feasible nodes $n_m^s$ in the remaining WSN network             Add $n_m^s$ to $RM$           end if        end for end for return the physical node failure recovery successfully