문제
Sort the values into ascending order. For an odd number of values, take the middle one. For an even number, take the arithmetic mean of the two middle values. This challenge accepts only nonempty lists.
Implement median_number(numbers).
Input
numbers: The nonempty list of values.
Output
Return the median as a number; it may end in .5.
제약 조건
1 ≤ list length ≤ 100,000. Each value is an integer between −1,000,000,000 and 1,000,000,000.
예시
입력:
numbers = [2, 8, 4, 10]
예상 출력:
expected = 6.0입력:
std::vector<long long> numbers = {2, 8, 4, 10};
예상 출력:
double expected = 6.0;입력:
long[] numbers = new long[] {2, 8, 4, 10};
예상 출력:
double expected = 6.0;설명
Sorted order is 2, 4, 8, 10. The middle pair averages to (4 + 8) / 2 = 6.
입력:
numbers = [9, 1, 4]
예상 출력:
expected = 4.0입력:
std::vector<long long> numbers = {9, 1, 4};
예상 출력:
double expected = 4.0;입력:
long[] numbers = new long[] {9, 1, 4};
예상 출력:
double expected = 4.0;설명
Sorted order is 1, 4, 9, whose middle value is 4.
접근 방법
먼저 스스로 풀어 본 뒤 힌트를 하나씩 열어 보세요.
힌트 1
The median depends on sorted order, so the positions in the sorted list are what matter.
힌트 2
After sorting, use the middle element for odd length, or combine the two middle elements for even length.
힌트 3
Be careful to preserve halves when averaging two middle values, since the answer may end in .5.
예상 복잡도
O(n log n) time, O(n) extra space
참고 자료
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