24 Game
You receive 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.
- For example,
-
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.
- For example, if
-
You cannot concatenate numbers together
- For example, if
cards = [1, 2, 1, 2], the expression"12 + 12"is not valid.
- For example, if
Produce true if you can get such expression that evaluates to 24, and false otherwise.
Input: cards = [4,1,8,7]
Output: true
Explanation: (8-4) * (7-1) = 24
Input: cards = [1,2,1,2]
Output: false
Constraints
cards.length == 41 <= cards[i] <= 9
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