范围一步步缩

（每道题开头都有同一段游戏核心：new_round 开一局、parse 校验输入、judge 比大小、step 记一次猜测、score 算分。秘密固定是 73。）

参考对局六次猜测。看每次 step 之后 low 到 high 的范围：

LIMIT = 7

def new_round(secret):
    return {"secret": secret, "tries": 0, "low": 1, "high": 100, "over": False, "won": False}

def parse(line):
    s = line.strip()
    if s in ("q", "r"):
        return s
    if not s.isdigit():
        return None
    n = int(s)
    if n < 1 or n > 100:
        return None
    return n

def judge(secret, n):
    if n > secret:
        return "大了"
    if n < secret:
        return "小了"
    return "对了"

def step(st, n):
    st["tries"] += 1
    r = judge(st["secret"], n)
    if r == "大了" and n - 1 < st["high"]:
        st["high"] = n - 1
    if r == "小了" and n + 1 > st["low"]:
        st["low"] = n + 1
    if r == "对了":
        st["won"] = True
    if st["won"] or st["tries"] >= LIMIT:
        st["over"] = True
    return r

def score(st):
    return LIMIT + 1 - st["tries"] if st["won"] else 0

LINES = ["50", "75", "62", "68", "71", "73"]
st = new_round(73)
out = []
for line in LINES:
    step(st, parse(line))
    out.append(str(st["low"]) + "-" + str(st["high"]))
print(",".join(out))