Watch 10 video solutions for 24 Game, a hard level problem involving Array, Math, Backtracking. This walkthrough by Sahil & Sarra has 512,507 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
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:
'/' represents real division, not integer division.
4 / (1 - 2 / 3) = 4 / (1 / 3) = 12.'-' as a unary operator.
cards = [1, 1, 1, 1], the expression "-1 - 1 - 1 - 1" is not allowed.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 == 41 <= cards[i] <= 9