ParseArrays

This code is along-with a blog post which lists a possible way to parse random( N dimensional) arrays.

Motivation :

Recently at work, I was working on this problem which incuded parsing a nested array type structure.

Example : 
.data = {
    {
        name1,
        {
            phone_number_1, 
            address_1,
            roll_number_1
        }
    },
    {
        name2,
        {
            phone_number_2, 
            address_2,
            roll_number_2
        }
    }    
}

The crux of the problem is to parse this .data into a list([]) which can be indexed, modified, appended to later.

Possible Approaches

• For illustration purposes, lets take .data = "{name,{name,{jalotra, shivam, machine}}}"

• First one that came to mind is to use ast.literal_eval() that ast module gives out of the bat.
  • Just as it is .data will give errors but if we change values to string types, it would work.

My Solution

• I have been leetcoding for sometime now, so I wanted to see if I could be able to come up with some algorithm to solve this problem on my own (read without looking how ast.literal_eval) works.

• Algorithm :

  • We start with a root node.

  • And for every open_parentheses a new node in this tree rooted at Root is created.

  • Now the structure that you describe for this node can be used recursively. I call this structure NArrayTree

  • And you can keep on adding the current value (string) this NArrayTree node can hold, like if the example was { jalotra, { ... something here } } first you encounter a opening bracket { and you will create a new Node NArrayTree([]) and till jalotra, you will append chars to this node.

  • Finally, your original node will look like NArrayTree(['j', 'a', 'l', 'o', 't', 'r', 'a']) and then once more you encounter a { do same for child node recursively.

  • After making this tree, you are left will parsing this tree, which is a trivial algo that uses dfs or give me the answer for children.

    # Parses tree starting at this node 
    # A assumption is that only leaf nodes will have values.
    def parse_tree(self):       
        res = []
        if len(self.value) > 0:
            for x in self.get_value():
                res.append(x)
    
        for child in self.children:
            res.append(child.parse_tree())
        return res
    

Examples :

1. • data = "{name}"
   • result = ["name"]

2. • data = "{name, section}"
   • result = ["name", "section"]

3. • data = "{name, {section}}"
   • result = ["name", ["section"]]

4. • data = "{name, {section, gender, {medadata, {XII, India}}}}"
   • result = ['name', ['section', 'gender', ['medadata', ['XII', 'India']]]]

5. • data(Original Problem) = { { name1, { phone_number_1, address_1, roll_number_1 } }, { name2, { phone_number_2, address_2, roll_number_2 } } }'
   • result = [['name1', ['phone_number_1', 'address_1', 'roll_number_1']], ['name2', ['phone_number_2', 'address_2', 'roll_number_2']]]