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.<ul> <li>For example, <code>4 / (1 - 2 / 3) = 4 / (1 / 3) = 12</code>.</li> </ul> </li> <li>Every operation done is between two numbers. In particular, we cannot use <code>'-'</code> as a unary operator. <ul> <li>For example, if <code>cards = [1, 1, 1, 1]</code>, the expression <code>"-1 - 1 - 1 - 1"</code> is <strong>not allowed</strong>.</li> </ul> </li> <li>You cannot concatenate numbers together <ul> <li>For example, if <code>cards = [1, 2, 1, 2]</code>, the expression <code>"12 + 12"</code> is not valid.</li> </ul> </li>
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 == 41 <= cards[i] <= 9