Day 1: Quartile

HackerRank 10 days of statistics

: Day 1 note taking

Quartile(4분위수): The quartiles of an ordered data set at the 3 points that split the data set into 4 equal groups.

- the odd number of elements

median of lower half from median = first quartile

median(중앙값) = second quartile = 50 percentile

median of upper half median = third quartile

- the even number of elements

			average of these two elements = median = second quartile
	an average of these two elements = a median of the lower half of median = first quartile
					an average of these two elements = a median of the upper half of median = third quartile

def median(arr):
    n = len(arr)
    if n%2==0:
        return (arr[int(n/2)-1]+arr[int(n/2)])//2
    else:
        return arr[int(n/2)]

def quartile(arr, N):
    first = median(arr[:N//2])
    second = median(arr)
    if N%2 == 0:
        third = median(arr[N//2:])
    else:
        third = median(arr[N//2+1:])
    return first, second, third
    

N = int(input())
arr = sorted(map(int,input().split()))


Q1, Q2, Q3 = quartile(arr, N)

quartile
Q1	Q1 >= 25% of the data
Q2	Q2 >= 50% of the data
Q3	Q3 >= 75% of the data