Triangle Classification

Classify three side lengths as invalid, equilateral, isosceles, or scalene. A valid triangle has positive sides, and its two shortest sides must sum to more than its longest side. Equal-to is invalid: it forms a straight line. Use equilateral for three equal sides, isosceles for exactly two, and scalene for three different sides.

Implement triangle_classification(sides).

Input

sides: The three side lengths in any order.

Output

Return one lowercase label: invalid, equilateral, isosceles, or scalene.

제약 조건

Exactly three integer sides, each between −1,000,000,000 and 1,000,000,000. Nonpositive sides are invalid.

예시

입력:
sides = [5, 5, 8]

예상 출력:
expected = "isosceles"

입력:
std::vector<long long> sides = {5, 5, 8};

예상 출력:
std::string expected = "isosceles";

입력:
long[] sides = new long[] {5, 5, 8};

예상 출력:
string expected = "isosceles";

입력:
sides = [1, 2, 3]

예상 출력:
expected = "invalid"

입력:
std::vector<long long> sides = {1, 2, 3};

예상 출력:
std::string expected = "invalid";

입력:
long[] sides = new long[] {1, 2, 3};

예상 출력:
string expected = "invalid";

참고 자료

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• Exercism: Triangle