Resistant dichotomic search P33412

Write an efficient function

    bool resistant_search(double x, const vector<double>& v);

that tells if @x@ belongs to the vector @v@ or not.

Precondition

The vector @v@ is “almost sorted” in nondecreasing order, in the sense that there may be at most a pair of indices $i$ and $j$ such that $0 \le i < j < n$ and @V@[$i$] $>$ @V@[$j$].

Observation

You only need to submit the required procedure; your main program will be ignored.