Gustav (Python 2)

This is a pretty straight forward meta strategy, shamelessly copied from one of my old answers in a similar KotH challenge. It considers a few simple strategies, looks how they would have performed over all previous rounds, and then follows the highest scoring one for the next round.

def choose(k, N, h):
    if k<2: return 999
    H = [[int(x) for x in l.split()] for l in h]
    score = lambda x,l: sum(abs(x-y)**.5 for y in l)
    S = [range(1,1000)
         + [max(range(1,1000), key=lambda x: score(x, H[i-1]))]
         + [max(range(1,1000), key=lambda x: score(x, H[i-2]))]
         + [min(range(1,1000), key=lambda x: score(x, H[i-1]))]
         + [min(range(1,1000), key=lambda x: score(x, H[i-2]))]
         for i in range(2,k+1)]
    scores = [sum(score(s[j],l) for s,l in zip(S[:-1], H[2:]))
              for j in range(len(S[0]))]
    return max(zip(scores, S[-1]))[1]

I realize now that the algorithm still has some flaws. E.g. it might keep "chasing itself" because it does not distinguish its own moves from those of the opponents. However, I'll leave it like this for now.