Instantly share code, notes, and snippets.

# hellman/beelzemon_solver.py

Created October 10, 2016 15:15
Show Gist options
• Save hellman/6c7349d3313493a198bd2d0c7f8c714c to your computer and use it in GitHub Desktop.
HITCON QUALS 2016 - Beelzemon (PPC 150)
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
 #!/usr/bin/env python #-*- coding:utf-8 -*- from sock import Sock def find_greedy(s): a, b = [], [] sa = sb = 0 for x in sorted(s, reverse=True, key=abs): if abs(sa + x - sb) < abs(sb + x - sa): a.append(x) sa += x else: b.append(x) sb += x while len(a) < len(b): a.append(b.pop()) while len(a) > len(b): b.append(a.pop()) if sum(a) == sum(b): return a return find_random(s, a, b) def find_swap(a, b, sa, sb): i = j = 0 best = (0, 0) best_sa = -999999999999999 wanted_sa = (sa + sb) / 2 while i < len(a) and j < len(b): test_sa = sa + b[j] - a[i] if abs(test_sa - wanted_sa) < abs(best_sa - wanted_sa): best = i, j best_sa = test_sa if test_sa < wanted_sa: j += 1 elif test_sa > wanted_sa: i += 1 elif test_sa == wanted_sa: if i < len(a) - 1: i += 1 else: j += 1 return best def move(a, i): while i > 0 and a[i] < a[i-1]: a[i-1], a[i] = a[i], a[i-1] i -= 1 while i < len(a) - 1 and a[i] > a[i+1]: a[i+1], a[i] = a[i], a[i+1] i += 1 def find_random(s, a, b): wanted = sum(s) / 2 sa, sb = sum(a), sum(b) a = sorted(a) b = sorted(b) bad_itr = 0 prev = 0 while 1: i, j = find_swap(a, b, sa, sb) sa = sa - a[i] + b[j] sb = sb - b[j] + a[i] a[i], b[j] = b[j], a[i] move(a, i) move(b, j) print n, k, len(s), "sa", sa, wanted, abs(sa - wanted) if sa == wanted: return a if abs(sa - wanted) >= prev: bad_itr += 1 if bad_itr == 10: print "----" break else: bad_itr = 0 prev = abs(sa - wanted) f = Sock("52.198.217.117 6666") itr = 0 while 1: itr += 1 try: res = f.read_line() n, k = map(int, res.split()) except Exception as err: print "Flag?", err, res, `f.buf` quit() print "#%d: %d %d" % (itr, n, k) s = range(-2**n, 2**n) if k & 1: invmap = {x**k: x for x in s} else: invmap = {x**k: -abs(x) for x in s} sk = sorted([x**k for x in s], key=abs) print "solving.." res = find_greedy(sk) assert res, "failed :(" ans = [] for x in res: ans.append(invmap[x]) if k % 2 == 0: invmap[x] *= -1 assert sum(x**k for x in ans) == sum(sk) / 2 vec = " ".join(map(str, ans)) f.send_line(vec) for n in xrange(1, 21): for k in xrange(1, n + 1): s = range(-2**n, 2**n) sk = sorted([x**k for x in s],key=abs) if k & 1: invmap = {x**k: x for x in s} else: invmap = {x**k: -abs(x) for x in s} print n, k res = find_greedy(sk) assert res, "failed :(" ans = [] for x in res: ans.append(invmap[x]) if k % 2 == 0: invmap[x] *= -1 assert sum(x**k for x in ans) == sum(sk) / 2