Program to check whether we can split list into consecutive increasing sublists or not in Python

Suppose we have a list of numbers called nums and that is sorted in non-decreasing order, we have to check whether it can be split into any number of subsequences such that each subsequence has at minimum length of 3 and that is consecutively increasing.

So, if the input is like nums = [2, 3, 4, 4, 5, 6, 7], then the output will be True, as we can split the list to [2, 3, 4] and [4, 5, 6, 7].

To solve this, we will follow these steps −

• counts := A map that contains elements of nums and its counts
• starts := a new list
• ends := a new list
• for each x in the items of the count in sorted order, do
  • if count[x] > count[x - 1], then
    • l := list of size (count[x] - count[x - 1]) and fill with x
    • insert l into starts
  • if count[x] > count[x + 1], then
    • l := list of size (count[x] - count[x + 1]) and fill with x
    • insert l into starts
• return true when all (start, end) pair satisfies (start + 2 <= end), otherwise return false

Example (Python)

Let us see the following implementation to get better understanding −

 Live Demo

from collections import Counter
class Solution:
   def solve(self, nums):
      count = Counter(nums)
      starts = []
      ends = []
      for x in sorted(count):
         if count[x] > count[x - 1]:
            starts.extend([x] * (count[x] - count[x - 1]))
         if count[x] > count[x + 1]:
            ends.extend([x] * (count[x] - count[x + 1]))
      return all(s + 2 <= e for s, e in zip(starts, ends))
ob = Solution()
nums = [2, 3, 4, 4, 5, 6, 7]
print(ob.solve(nums))

Input

[6, 7, 5, 10, 13], 2

Output

True

Arnab Chakraborty

Updated on: 12-Dec-2020

254 Views

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