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.
cards.length == 41 <= cards[i] <= 9