3305. Count of Substrings Containing Every Vowel and K Consonants I
Description
You are given a string word
and a non-negative integer k
.
Return the total number of substrings of word
that contain every vowel ('a'
, 'e'
, 'i'
, 'o'
, and 'u'
) at least once and exactly k
consonants.
Example 1:
Input: word = "aeioqq", k = 1
Output: 0
Explanation:
There is no substring with every vowel.
Example 2:
Input: word = "aeiou", k = 0
Output: 1
Explanation:
The only substring with every vowel and zero consonants is word[0..4]
, which is "aeiou"
.
Example 3:
Input: word = "ieaouqqieaouqq", k = 1
Output: 3
Explanation:
The substrings with every vowel and one consonant are:
word[0..5]
, which is"ieaouq"
.word[6..11]
, which is"qieaou"
.word[7..12]
, which is"ieaouq"
.
Constraints:
5 <= word.length <= 250
word
consists only of lowercase English letters.0 <= k <= word.length - 5
Solutions
Solution 1: Problem Transformation + Sliding Window
We can transform the problem into solving the following two subproblems:
- Find the total number of substrings where each vowel appears at least once and contains at least $k$ consonants, denoted as $\textit{f}(k)$;
- Find the total number of substrings where each vowel appears at least once and contains at least $k + 1$ consonants, denoted as $\textit{f}(k + 1)$.
Then the answer is $\textit{f}(k) - \textit{f}(k + 1)$.
Therefore, we design a function $\textit{f}(k)$ to count the total number of substrings where each vowel appears at least once and contains at least $k$ consonants.
We can use a hash table $\textit{cnt}$ to count the occurrences of each vowel, a variable $\textit{ans}$ to store the answer, a variable $\textit{l}$ to record the left boundary of the sliding window, and a variable $\textit{x}$ to record the number of consonants in the current window.
Traverse the string. If the current character is a vowel, add it to the hash table $\textit{cnt}$; otherwise, increment $\textit{x}$ by one. If $\textit{x} \ge k$ and the size of the hash table $\textit{cnt}$ is $5$, it means the current window meets the conditions. We then move the left boundary in a loop until the window no longer meets the conditions. At this point, all substrings ending at the right boundary $\textit{r}$ and with the left boundary in the range $[0, .. \textit{l} - 1]$ meet the conditions, totaling $\textit{l}$ substrings. We add $\textit{l}$ to the answer. Continue traversing the string until the end, and we get $\textit{f}(k)$.
Finally, we return $\textit{f}(k) - \textit{f}(k + 1)$.
The time complexity is $O(n)$, where $n$ is the length of the string $\textit{word}$. The space complexity is $O(1)$.
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