Syntax error Program to find the length of longest substring which has two distinct elements in Python

Program to find the length of longest substring which has two distinct elements in Python

Suppose we have a string s, we have to find the length of the longest substring that contains at most 2 distinct characters.

So, if the input is like s = "xyzzy", then the output will be 4, as "yzzy" is the longest substring with at most 2 unique characters.

To solve this, we will follow these steps−

  • start := 0

  • c := a map

  • ans := 0

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

    • c[s[end]] := c[s[end]] + 1

    • while size of c > 2, do

      • c[s[start]] := c[s[start]] - 1


      • if c[s[start]] is 0, then

        • delete c[s[start]]

      • start := start + 1

    • ans := maximum of ans and (end - start + 1)

  • return ans

Let us see the following implementation to get better understanding −

Example

 Live Demo

class Solution:
   def solve(self, s):
      from collections import Counter
      start = 0
      c = Counter()
      ans = 0
      for end in range(len(s)):
         c[s[end]] += 1
         while len(c) > 2:
            c[s[start]] -= 1
            if not c[s[start]]:
               del c[s[start]]
            start += 1
         ans = max(ans, end - start + 1)
      return ans
ob = Solution()
s = "xyzzy"
print(ob.solve(s))

Input

s = "xyzzy"

Output

4
Updated on: 2020-10-10T13:57:29+05:30

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