# Integers K, M and a non-empty array A consisting of N integers, not bigger than M, are given.
# 
# The leader of the array is a value that occurs in more than half of the elements of the array, and the segment of the array is a sequence of consecutive elements of the array.
# 
# You can modify A by choosing exactly one segment of length K and increasing by 1 every element within that segment.
# 
# The goal is to find all of the numbers that may become a leader after performing exactly one array modification as described above.
# 
# Write a function:
# 
# def solution(k, m, a)
# 
# that, given integers K and M and an array A consisting of N integers, returns an array of all numbers that can become a leader, after increasing by 1 every element of exactly one segment of A of length K. The returned array should be sorted in ascending order, and if there is no number that can become a leader, you should return an empty array. Moreover, if there are multiple ways of choosing a segment to turn some number into a leader, then this particular number should appear in an output array only once.
# 
# For example, given integers K = 3, M = 5 and the following array A:
# 
#   A[0] = 2
#   A[1] = 1
#   A[2] = 3
#   A[3] = 1
#   A[4] = 2
#   A[5] = 2
#   A[6] = 3
# the function should return [2, 3]. If we choose segment A[1], A[2], A[3] then we get the following array A:
# 
#   A[0] = 2
#   A[1] = 2
#   A[2] = 4
#   A[3] = 2
#   A[4] = 2
#   A[5] = 2
#   A[6] = 3
# and 2 is the leader of this array. If we choose A[3], A[4], A[5] then A will appear as follows:
# 
#   A[0] = 2
#   A[1] = 1
#   A[2] = 3
#   A[3] = 2
#   A[4] = 3
#   A[5] = 3
#   A[6] = 3
# and 3 will be the leader.
# 
# And, for example, given integers K = 4, M = 2 and the following array:
# 
#   A[0] = 1
#   A[1] = 2
#   A[2] = 2
#   A[3] = 1
#   A[4] = 2
# the function should return [2, 3], because choosing a segment A[0], A[1], A[2], A[3] and A[1], A[2], A[3], A[4] turns 2 and 3 into the leaders, respectively.
# 
# Write an efficient algorithm for the following assumptions:
# 
# N and M are integers within the range [1..100,000];
# K is an integer within the range [1..N];
# each element of array A is an integer within the range [1..M].

# K := integer
# M := integer
# A := Array of N integers where n in 1..M
require 'set'

def solution(k, m, a)
  # results
  res = Set.new
  
  # arrays of arrays
  subs = []
  
  # 1. create sub-arrays
  (a.size - k + 1).times do |idx|
    subs.push [idx, idx+k-1]
  end
  
  # 2. increase sub-arrays
  # 3. ... and count values
  subs.each do |left, right|
    count = {}
    mod = a.clone.map.with_index do |v, idx|
      if idx >= left and idx <= right
        count[v+1] ||= 0
        count[v+1] += 1
        v += 1
      else
        count[v] ||= 0
        count[v] += 1
        v
      end
    end
    m = count.keys.max_by {|k| count[k]}

    res.add(m)
    mod 
  end
  res.to_a
end