問題
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.
制約
1 ≤ list length ≤ 100,000. Each value is an integer between −1,000,000,000 and 1,000,000,000.
例
入力：
numbers = [2, 8, 4, 10]
期待される出力：
expected = 6.0入力：
std::vector<long long> numbers = {2, 8, 4, 10};
期待される出力：
double expected = 6.0;入力：
long[] numbers = new long[] {2, 8, 4, 10};
期待される出力：
double expected = 6.0;解説
Sorted order is 2, 4, 8, 10. The middle pair averages to (4 + 8) / 2 = 6.
入力：
numbers = [9, 1, 4]
期待される出力：
expected = 4.0入力：
std::vector<long long> numbers = {9, 1, 4};
期待される出力：
double expected = 4.0;入力：
long[] numbers = new long[] {9, 1, 4};
期待される出力：
double expected = 4.0;解説
Sorted order is 1, 4, 9, whose middle value is 4.
解き方のヒント
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
The median depends on sorted order, so the positions in the sorted list are what matter.
ヒント 2
After sorting, use the middle element for odd length, or combine the two middle elements for even length.
ヒント 3
Be careful to preserve halves when averaging two middle values, since the answer may end in .5.
目安の計算量
O(n log n) time, O(n) extra space
参考資料
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。