Second Largest Value

Problema

Return the second largest distinct value in the list. Repeated values count once.

Implement second_largest(numbers).

numbers: A list of non-negative integers.

Return the second largest distinct value, or -1 if it doesn't exist.

0 ≤ length ≤ 100,000; 0 ≤ each value ≤ 10⁹

Ejemplo 1

Entrada:
numbers = [4, 9, 7, 9]

Salida esperada:
expected = 7

Entrada:
std::vector<long long> numbers = {4, 9, 7, 9};

Salida esperada:
long long expected = 7;

Entrada:
long[] numbers = new long[] {4, 9, 7, 9};

Salida esperada:
long expected = 7;

Distinct values are 9, 7, 4; the second largest is 7.

Ejemplo 2

Entrada:
numbers = [5, 5]

Salida esperada:
expected = -1

Entrada:
std::vector<long long> numbers = {5, 5};

Salida esperada:
long long expected = -1;

Entrada:
long[] numbers = new long[] {5, 5};

Salida esperada:
long expected = -1;

Only one distinct value exists, so the answer is -1.

Inténtalo primero por tu cuenta y luego abre las pistas una a una.

Pista 1

You need the largest and the next different value, not just the top two positions.

Pista 2

Track two distinct maxima as you scan, updating them when a new value fits above or between them.

Pista 3

If no second distinct value ever appears, return the special fallback value.

Complejidad esperada

O(n) time, O(1) extra space

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