Program to find minimum number of monotonous string groups in Python

PythonServer Side ProgrammingProgramming

Suppose we have a lowercase string s. We have to find the minimum numbers of contiguous substrings in which s is divided into parts such that each substring is either non-increasing or non-decreasing. So for example, if the string is like "pqqqr" is a non-decreasing string, and "qqqp" is a non-increasing string.

So, if the input is like s = "pqrsrqp", then the output will be 2, because we can break s like "pqrs" and "rqp".

To solve this, we will follow these steps −

  • if s is empty, then

    • return 0

  • last := s[0]

  • direction := 1

  • count := 1

  • for each char in s, do

    • if char > last, then

      • if direction is same as 1, then

        • direction := 0

      • otherwise when direction is same as 2, then

        • direction := 1

        • count := count + 1

    • otherwise when char < last, then

      • if direction is same as 1, then

        • direction := 2

      • otherwise when direction is same as 0, then

        • direction := 1

        • count := count + 1

    • last := char

  • return count

Example

Let us see the following implementation to get better understanding

def solve(s):
   if not s:
      return 0

   last = s[0]
   direction = 1
   count = 1

   for char in s:
      if char > last:
         if direction == 1:
            direction = 0
         elif direction == 2:
            direction = 1
            count += 1
      elif char < last:
         if direction == 1:
            direction = 2
         elif direction == 0:
            direction = 1
            count += 1
      last = char

   return count

s = "pqrsrqp"
print(solve(s))

Input

"pqrsrqp"

Output

2
raja
Updated on 12-Oct-2021 11:23:33

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