First occurrence P84219

Statement

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Write an efficient function

int first_occurrence(double x, const vector<double>& v);

that returns the position of the first occurrence of x in the vector v. If x does not belong to v, return a -1.

Precondition

The vector v is sorted in nondecreasing order.

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

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