Lesson4. Counting Elements - PermCheck

PermCheck - Check whether array A is a permutation.

https://app.codility.com/programmers/lessons/4-counting_elements/perm_check/

문제요약

N개의 정수 배열 A가 있을 때, 1부터 N까지 한 번씩 나오면 permutation이라고 한다. A가 permutation이면 1, 아니면 0을 반환

Assume that:

N is an integer within the range [1..100,000];

each element of array A is an integer within the range [1..1,000,000,000].

Complexity:

expected worst-case time complexity is O(N);

expected worst-case space complexity is O(N) (not counting the storage required for input arguments).

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