s only consists of a , b or _c _characters.

Solution

Method 1 - Sliding Window

To solve this problem, we can use the sliding window technique, which is efficient for this type of substring problem.

A substring containing all three characters starting at an index start and ending at index end will also contain all three characters if it ends at any index beyond end.

Approach

Use a sliding window approach with two pointers (start and end) to traverse the string.
Maintain a count of characters ('a', 'b', and 'c') in the current window using a frequency map or an array.
Expand the window by moving the end pointer, adding characters to the count.
Once the window contains at least one occurrence of 'a', 'b', and 'c', calculate the valid substrings ending at end. The count of these substrings is (n - end), where n is the length of the string. Move the start pointer to shrink the window and continue this process.
Repeat until the window can no longer contain all three characters.

Code

[{"language":"Java","code":"class Solution {\n    public int numberOfS

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