2953. Count Complete Substrings

Problem Link

Description

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You are given a string word and an integer k.

A substring s of word is complete if:

• Each character in s occurs exactly k times.
• The difference between two adjacent characters is at most 2. That is, for any two adjacent characters c1 and c2 in s, the absolute difference in their positions in the alphabet is at most 2.

Return the number of complete substrings of word.

A substring is a non-empty contiguous sequence of characters in a string.

 

Example 1:

Input: word = "igigee", k = 2
Output: 3
Explanation: The complete substrings where each character appears exactly twice and the difference between adjacent characters is at most 2 are: igigee, igigee, igigee.

Example 2:

Input: word = "aaabbbccc", k = 3
Output: 6
Explanation: The complete substrings where each character appears exactly three times and the difference between adjacent characters is at most 2 are: aaabbbccc, aaabbbccc, aaabbbccc, aaabbbccc, aaabbbccc, aaabbbccc.

 

Constraints:

• 1 <= word.length <= 105
• word consists only of lowercase English letters.
• 1 <= k <= word.length

Solution

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Python3

class Solution:
    def countCompleteSubstrings(self, word: str, k: int) -> int:
 
        def f(x):
            return ord(x) - ord('a')
        
        def check(cnt, uniqueChars):
            unique = 0
 
            for x in cnt:
                if x == 0: continue
                if x != k: return False
                unique += 1
 
            return unique == uniqueChars
 
        def solve(A):
            M = len(A)
            res = 0
 
            # there are 26 unique characters, loop thru the len with k, 2k, 3k ..., 26k
            for uniqueChars in range(1, 27):
                length = k * uniqueChars
                if length > M: break
 
                cnt = [0] * 26
                for i in range(length):
                    cnt[f(A[i])] += 1
                
                res += check(cnt, uniqueChars)
 
                # when length is greater than M, slide the window from (length - M, length)
                for i in range(length, M):
                    cnt[f(A[i - length])] -= 1
                    cnt[f(A[i])] += 1
                    res += check(cnt, uniqueChars)
            
            return res
 
 
        N = len(word)
        res = 0
        curr = ""
 
        for i, x in enumerate(word):
            curr += x
 
            if i < N - 1 and abs(ord(word[i + 1]) - ord(word[i])) > 2:
                res += solve(curr)
                curr = ""
        
        res += solve(curr)
 
        return res