Code Fights - arrayChange

README.md

You are given an array of integers. On each move you are allowed to increase exactly one of its element by one. Find the minimal number of moves required to obtain a strictly increasing sequence from the input.

Example

For inputArray = [1, 1, 1], the output should be
arrayChange(inputArray) = 3.

Input/Output

• [time limit] 4000ms (py3)

• [input] array.integer inputArray

  Guaranteed constraints:

  3 ≤ inputArray.length ≤ 105,
  -105 ≤ inputArray[i] ≤ 105.
  

• [output] integer

  • The minimal number of moves needed to obtain a strictly increasing sequence from inputArray.
  • It's guaranteed that for the given test cases the answer always fits signed 32-bit integer type.

array_change.py

from typing import List


class ArrayChange:
    @classmethod
    def array_change(cls, data: List[int]):
        increments = 0
        prev = data[0] - 1
        for d in data:
            if prev - d >= 0:
                increment = prev - d + 1
                increments += increment
                d += increment
            prev = d
        return increments

arrayChange.py

def arrayChange(data: list):
    increments = 0
    prev = data[0] - 1
    for d in data:
        if prev - d >= 0:
            increment = prev - d + 1
            increments += increment
            d += increment
        prev = d
    return increments

test_array_change.py

import unittest
from array_change import ArrayChange


class TestArrayChange(unittest.TestCase):
    def test_1(self):
        input_array = [1, 1, 1]
        solution = 3
        result = ArrayChange.array_change(input_array)
        self.assertEqual(result, solution)

    def test_2(self):
        input_array = [-1000, 0, -2, 0]
        solution = 5
        result = ArrayChange.array_change(input_array)
        self.assertEqual(result, solution)

    def test_3(self):
        input_array = [2, 1, 10, 1]
        solution = 12
        result = ArrayChange.array_change(input_array)
        self.assertEqual(result, solution)

    def test_4(self):
        input_array = [2, 3, 3, 5, 5, 5, 4, 12, 12, 10, 15]
        solution = 13
        result = ArrayChange.array_change(input_array)
        self.assertEqual(result, solution)


if __name__ == '__main__':
    unittest.main()