Derek's 93

p93.py

import itertools

# using reverse polish notation

def calculate(expr):
  stack = list()
  for e in expr:
    if type(e) == int:
      stack.append(e)
    else:
      b, a = stack.pop(), stack.pop()
      if e == "+":
        stack.append(a + b)
      elif e == "-":
        stack.append(a - b)
      elif e == "*":
        stack.append(a * b)
      elif e == "/":
        if b == 0:
          return float(-0.5) # hack
        stack.append(a / float(b))

  return float(stack[0])

def solve():
  solns = list()
  for nums in itertools.combinations(range(1,10), 4):
    ans = list()
    for combs in itertools.permutations(nums, 4):
      for opss in itertools.combinations_with_replacement(("+", "-", "*", "/"), 3):
        for ops in itertools.permutations(opss, 3):
          poss = [
            combs + ops,
            combs[:3] + (ops[0], ) + (combs[3], ) + ops[1:],
            combs[:3] + ops[:2] + (combs[3], ) + (ops[2], ),
            combs[:2] + (ops[0], ) + (combs[2], ) + (ops[1], ) + (combs[3], ) + (ops[2], ),
            combs[:2] + (ops[0], ) + combs[2:] + ops[1:]
          ]
          for p in poss:
            res = calculate(p)
            if res.is_integer():
              ans.append(int(res))

    # finding the highest consecutive in the list
    for x in xrange(1, (max(ans)+2)):
      if x not in ans:
        solns.append(((x-1), nums))
        break
  return solns

print max(solve())