Syntax error Program to find minimum string size that contains given substring in Python

Program to find minimum string size that contains given substring in Python

Suppose we have two strings s and t, we have to find the size of a minimum substring in s that contains all the characters of t. If there is no such substring exists then return -1.

So, if the input is like s = "thegrumpywizardmakes" t = "wake", then the output will be 10, as the shortest substring that contains "wake" is "wizardmake" (length of 10).

To solve this, we will follow these steps −

  • counter := frequency of each character in b

  • start := 0

  • min_subs := inf

  • rem := count of distinct characters in b

  • for end in range 0 to size of a, do

    • current := a[end]

    • if current is in counter, then

      • counter[current] := counter[current] - 1

      • if counter[current] is same as 0, then

        • rem := rem - 1

    • while rem is same as 0, do

      • prev_char := a[start]

      • if prev_char is in counter, then

        • counter[prev_char] := counter[prev_char] + 1

        • if counter[prev_char] > 0, then

          • rem := rem + 1

      • min_subs := minimum of min_subs and (end - start + 1)

      • start := start + 1

  • return min_subs when min_subs is not inf otherwise -1

Example (Python)

Let us see the following implementation to get better understanding −

class Solution:
   def solve(self, a, b):
      counter = {}
      for char in b:
         counter[char] = counter.get(char, 0) + 1
      start = 0
      min_subs = float("inf")
      rem = len(counter)
      for end in range(len(a)):
         current = a[end]
         if current in counter:
            counter[current] -= 1
            if counter[current] == 0:
               rem -= 1
         while rem == 0:
            prev_char = a[start]
            if prev_char in counter:
               counter[prev_char] += 1
               if counter[prev_char] > 0:
                  rem += 1
               min_subs = min(min_subs, end - start + 1)
               start += 1
      return min_subs if min_subs != float("inf") else -1
ob = Solution()
s = "thegrumpywizardmakes"
t = "wake"
print(ob.solve(s, t))

Input

"thegrumpywizardmakes", "wake"

Output

2
Updated on: 2020-12-21T14:08:50+05:30

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