harsh/data-structures: Codes for data structures and algorithms in python. @ 8f8cb630828f65ada1ca4a7a11df9882dca50162

Problem 1

Given an array, find out the product of its element using recursion.

Input: [1, 2, 3, 4, 5]
Output: 120

def product(arr):
    """
    calculates the product of all the numbers in array
    """
    if len(arr) == 0:
        return 1
    else:
        return len(arr) * product(arr[1:])

product([1, 2, 3, 4, 5])

Problem 2

Given a string, write a function reverse which accepts a string and returns a new string in reverse.

Input: reverse("Hello")
Output: "olleH"

def reverse(string):
    """
    returns the reverse of a string
    """
    if len(string) == 0:
        return ""
    return string[-1] + reverse(string[:-1])

reverse("Hello")

'olleH'

Problem 3

Given a string, write a function reverse to check whether the string is palindrome. Note: You must use recursion for this problem.

Input1: reverse("malayalam")
Output1: True
Input2: reverse("hello")
Output2: False

def reverse(string):
    """
    returns the reverse of a string
    """
    if len(string) == 0:
        return ""
    return string[-1] + reverse(string[:-1])

string = "malayalam"
string == reverse(string)

True

Problem 4

Given a nested array, write a function flatten to return a flatlist

Input: [[2, 3, [4]]]
Output: [2, 3, 4]

def flatten(arr):
    """
    returns the flattened array.
    """
    result = []
    for element in arr:
        if type(element) is list:
            result.extend(flatten(element))
        else:
            result.append(element)
    return result

flatten([[2, 3, [4]]])

[2, 3, 4]

Problem 5

Given a word list, write a function capitalize_first to capitalize the first letter of each string in the array. Note, you must use recursion for this problem.

Input: capitalize(["hello", "world"])
Output: ["Hello", "World]

def capitalize_first(arr):
    """
    converts the first letter of all the elements into uppercase.
    """
    result = []
    if len(arr) == 0:
        return result
    result.append(arr[0][0].upper() + arr[0][1:])
    return result + capitalize_first(arr[1:])

capitalize_first(["hello", "world"])

['Hello', 'World']

Problem 6

Given a .json object, write a function string_convert which takes an object and finds all the values which are numbers and converts them into a string.

Input: { "num" : 1, "data": {

"value" : 8,
"jam" : {
    "english": 50
}

} }

Output: { "num" : "1", "data": {

"value" : "8",
"jam" : {
    "english": "50"
}

} }

def string_convert(obj):
    """
    converts all the integer values inside of an object into a string.
    """
    for element in obj:
        if type(obj[element]) is int:
            obj[element] = str(obj[element])
        elif type(obj[element]) is dict:
            obj[element] = string_convert(obj[element])

    return obj

string_convert({
  "num" : 1,
  "data": {
      "value" : 8,
      "jam" : {
          "english": 50
      }
  }
})

{'num': '1', 'data': {'value': '8', 'jam': {'english': '50'}}}

Problem 7

Given a .json object, write a function fetch_str which takes the object and finds all the keys that have string values. Note, you must use recursion for this problem.

Input: {"Hello": "World",

    "England": {
        "London": "Heathrow",
        "Oxford":100,
        "Stanford": {
            "France": "Paris",
            "Germany": {
                "Berlin": "TU Berlin",
                "Frankfurt": 1000
            }
        }
    },
    "India": 1}

Output: ["Hello", "London", "France", "Berlin"]

def fetch_str(obj):
    """
    Returns keys with integer values.
    """
    result = []
    for element in obj:
        if type(obj[element]) is str:
            result.append(element)
        if type(obj[element]) is dict:
            result.extend(fetch_str(obj[element]))
    return result

fetch_str({"Hello": "World",
          "England": {
              "London": "Heathrow",
              "Oxford":100,
              "Stanford": {
                  "France": "Paris",
                  "Germany": {
                      "Berlin": "TU Berlin",
                      "Frankfurt": 1000
                  }
              }
          },
          "India": 1})

['Hello', 'London', 'France', 'Berlin']

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