[hackerrank] ML basic statistics warmup

# -*- coding: utf-8 -*-
import sys, collections, math

def mean(A):
    S = sum(A)
    N = len(A)
    return float(S) / float(N) if N > 0 else 0.0

def median(A):
    N = len(A)
    A_sorted = sorted(A)
    if N%2 != 0:
        ret = A_sorted[N/2]
    else:
        ret = float(A_sorted[N/2] + A_sorted[N/2-1])/2.0
    return ret

COUNT = 0
VALUE = 1

def mode_freq_cmp(v1, v2):
    if v1[COUNT] != v2[COUNT]:
        return v2[COUNT] - v1[COUNT]
    else:
        return v1[VALUE] - v2[VALUE]

def mode(A):
    freq = collections.defaultdict(int)

    for v in A:
        freq[v] += 1

    freq_list = [(count, value) for value, count in freq.iteritems()]
    freq_list.sort(cmp=mode_freq_cmp)

    return freq_list[0][VALUE]

def stdev(A):
    N = len(A)
    M = mean(A)
    S = 0
    for v in A:
        d = v - M
        S += d * d
    return math.sqrt( S / N )

def confidence_interval(A, Mean, Stdev, confidence=0.95):
    v = 1.96 *  Stdev / math.sqrt(len(A))
    return Mean - v, Mean + v

def main(A):
    Mean, Median, Stdev = mean(A), median(A), stdev(A)
    conf_intervals = confidence_interval(A, Mean, Stdev)
    print '%.1f' % Mean
    print '%.1f' % Median
    print '%d'   % mode(A)
    print '%.1f' % Stdev
    print '%.1f %.1f' % (conf_intervals[0], conf_intervals[1])

if __name__ == '__main__':
    N = int(input())
    A = [int(v) for v in sys.stdin.readline().split(' ')]
    #A = [int(v) for v in "64630 11735 14216 99233 14470 4978 73429 38120 51135 67060".split()]
    main(A)