Count the contiguous substrings of s that contain all three letters: a, b, and c. A letter may appear more than once. Substrings at different positions count separately, even if their text is identical.
Example 1:
Input: s = "abca"
Output: 3Explanation: The valid substrings are "abc", "bca", and "abca". Each contains at least one of a, b, and c.
Example 2:
Input: s = "aaab"
Output: 0Explanation: The string contains no "c", so none of its substrings can contain all three letters.
Example 3:
Input: s = "cabca"
Output: 6Explanation: There are three valid substrings starting at index 0 ("cab", "cabc", "cabca"), two starting at index 1 ("abc", "abca"), and one at index 2 ("bca").
Constraints:
3 <= s.length <= 50000- Each character is
a,b, orc.