number-of-substrings-containing-all-three-characters

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1358. Number of Substrings Containing All Three Characters (Medium)

Given a string s consisting only of characters a, b and c.

Return the number of substrings containing at least one occurrence of all these characters a, b and c.

 

Example 1:

Input: s = "abcabc"
Output: 10
Explanation: The substrings containing at least one occurrence of the characters a, b and c are "abc", "abca", "abcab", "abcabc", "bca", "bcab", "bcabc", "cab", "cabc" and "abc" (again). 

Example 2:

Input: s = "aaacb"
Output: 3
Explanation: The substrings containing at least one occurrence of the characters a, b and c are "aaacb", "aacb" and "acb". 

Example 3:

Input: s = "abc"
Output: 1

 

Constraints:

• 3 <= s.length <= 5 x 10^4
• s only consists of a, b or c characters.

Related Topics

[Hash Table] [String] [Sliding Window]

Hints

Hint 1

For each position we simply need to find the first occurrence of a/b/c on or after this position.

Hint 2

So we can pre-compute three link-list of indices of each a, b, and c.