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# File 'lib/pool_balancing.rb', line 2
def self.balance(values, nbpools)
values.sort! { |a,b| b[0] <=> a[0] }
pools = Array.new( nbpools ) { Array.new }
poolsum = Array.new( nbpools, 0 )
out = Array.new
ind = 0; dir = 1
values.each do |val|
pools[ind] << val
poolsum[ind] += val[0]
ind += dir;
if( ind == nbpools ) then ind = nbpools-1; dir = -1; end
if( ind == -1 ) then ind = 0; dir = 1; end
end
while out.length < (nbpools-1)
minmax = poolsum.each_with_index.minmax.map{ |t| t[1] }
diff = poolsum[minmax[1]] - poolsum[minmax[0]]
return pools.map { |p| p.map { |v| v[1] } } if diff <= 1 && out.empty?
ind = 0
delete = true
while ind < pools[minmax[1]].length && delete == true
maxval = pools[minmax[1]][ind][0]
minval = pools[minmax[0]][ind][0]
if (poolsum[minmax[1]] - 2 * maxval + 2 * minval - poolsum[minmax[0]]).abs < diff
pools[minmax[1]][ind][0] = minval
pools[minmax[0]][ind][0] = maxval
poolsum[minmax[1]] += (minval - maxval)
poolsum[minmax[0]] += (maxval - minval)
delete = false
pools.concat(out.pop) && out.clear unless out.empty?
end
ind+=1
end
out << pools.delete_at(minmax[0]) if delete
end
end
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