 Solution

ID: past-exam-of-the-year-1-of-the-computer-science-course-of-the-university-of-oxford/2014/imperative-programming/1/b/ii/solution

There are

N + 1 - p

candidate values in

[p, N + 1)

and exactly

N - k

occurrences there. If

k \geq p

, then

N - k \leq N - p < N + 1 - p .

Some value in [p, N + 1) is missing.

This conclusion does not assert that every value on the lower side is present; duplicates may leave both sides deficient.

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