CODEWITHSUNDEEP
crystal-lang
Durian_huang
Durian_huang

Reputation: 51

how to use crystal to defined a ListNode class

i used to use python to do it and i don't know how to defined a ListNode class by Crystal, what i do is just for the second problem in Leetcode website which is Add Two Number. i have tried in this way but i got undefined method 'next' for ListNode error message

class ListNode


    def initialize(x : Int32)

        @val = x
        @next = Nil

    end
end

def addTwoNumbers(l1 : ListNode, l2 : ListNode)

    divide_value = 0
    first = l1
    second = l2
    is2 = 0
    while True
        sum = l1.val + l2.val + divide_value
        residual_value = sum % 10
        l1.val = residual_value
        l2.val = residual_value
        divide_value = sum / 10

        if l1.next and l2.next
            l1 = l1.next
            l2 = l2.next

        elsif !l1.next and l2.next
            l1.val = 0
            l2 = l2.next
            is2 = 1

        elsif l1.next and !l2.next
            l2.val = 0
            l1 = l1.next
        else
            if is2
                if divide_value != 0
                    l2.next = ListNode.new divide_value
                    return second
                end
                return second
            else
                if divide_value != 0
                    l1.next = ListNode.new divide_value
                    return first
                end
                return first
            end
        end
    end

end

l1 = ListNode.new 1
l2 = ListNode.new 9
l2 = l2.next
l2 = ListNode.new 9
result = addTwoNumbers(l1,l2)
while result
    puts(result.val)
    result = result.next
end

can anyone help me?

Upvotes: 0

Views: 97

Answers (1)

halfelf
halfelf

Reputation: 10107

You need to create getter and setter method for instance variables, in order to access them.

https://crystal-lang.org/reference/syntax_and_semantics/methods_and_instance_variables.html

In your code, just add property:

class ListNode
    property val
    property next_node # avoiding `next`. It is a reserved keyword.

    def initialize(x : Int32)
        @val = x
        @next_node = Nil
    end
end

l2 = ListNode.new 9
l2 = l2.next_node  # ok now

Upvotes: 3

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