Problema
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.
Vincoli
1 ≤ list length ≤ 100,000. Each value is an integer between −1,000,000,000 and 1,000,000,000.
Esempi
Input:
numbers = [2, 8, 4, 10]
Output atteso:
expected = 6.0Input:
std::vector<long long> numbers = {2, 8, 4, 10};
Output atteso:
double expected = 6.0;Input:
long[] numbers = new long[] {2, 8, 4, 10};
Output atteso:
double expected = 6.0;Spiegazione
Sorted order is 2, 4, 8, 10. The middle pair averages to (4 + 8) / 2 = 6.
Input:
numbers = [9, 1, 4]
Output atteso:
expected = 4.0Input:
std::vector<long long> numbers = {9, 1, 4};
Output atteso:
double expected = 4.0;Input:
long[] numbers = new long[] {9, 1, 4};
Output atteso:
double expected = 4.0;Spiegazione
Sorted order is 1, 4, 9, whose middle value is 4.
Come affrontarlo
Prova prima da solo, poi apri un suggerimento alla volta.
Suggerimento 1
The median depends on sorted order, so the positions in the sorted list are what matter.
Suggerimento 2
After sorting, use the middle element for odd length, or combine the two middle elements for even length.
Suggerimento 3
Be careful to preserve halves when averaging two middle values, since the answer may end in .5.
Complessità attesa
O(n log n) time, O(n) extra space
Riferimenti
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