You are given an integer array `cards` of length `4`. You have four cards, each containing a number in the range `[1, 9]`. You should arrange the numbers on these cards in a mathematical expression using the operators `['+', '-', '*', '/']` and the parentheses `'('` and `')'` to get the value 24.

You are restricted with the following rules:

*   The division operator `'/'` represents real division, not integer division.
    *   For example, `4 / (1 - 2 / 3) = 4 / (1 / 3) = 12`.
*   Every operation done is between two numbers. In particular, we cannot use `'-'` as a unary operator.
    *   For example, if `cards = [1, 1, 1, 1]`, the expression `"-1 - 1 - 1 - 1 "` is **not allowed**.
*   You cannot concatenate numbers together
    *   For example, if `cards = [1, 2, 1, 2]`, the expression `"12 + 12 "` is not valid.

Return `true` if you can get such expression that evaluates to `24`, and `false` otherwise.

**Example 1:**

**Input:** cards = \[4,1,8,7\]
**Output:** true
**Explanation:** (8-4) \* (7-1) = 24

**Example 2:**

**Input:** cards = \[1,2,1,2\]
**Output:** false

**Constraints:**

*   `cards.length == 4`
*   `1 <= cards[i] <= 9`


from itertools import permutations


def helper(cards, target=24):
    if len(cards) == 1:
        return abs(cards[0] - target) < 1e-6

    for i in range(len(cards)):
        for j in range(i + 1, len(cards)):
            a, b = cards[i], cards[j]
            rest = [cards[k] for k in range(len(cards)) if k != i and k != j]
            for e in a + b, a - b, a * b, a / b:
                if helper(rest + [e]):
                    return True
    return False


def canGet24(cards):
    return helper(cards)
