Second Largest Value

問題

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

例 1

入力：
numbers = [4, 9, 7, 9]

期待される出力：
expected = 7

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

期待される出力：
long long expected = 7;

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

期待される出力：
long expected = 7;

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

例 2

入力：
numbers = [5, 5]

期待される出力：
expected = -1

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

期待される出力：
long long expected = -1;

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

期待される出力：
long expected = -1;

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

まずは自分で考えてから、ヒントを 1 つずつ開いてみましょう。

ヒント 1

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

ヒント 2

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

ヒント 3

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

目安の計算量

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

この課題はCodeUtility用に調整されています。上記の説明と制約に従ってください。