125.py

class Solution:
    def numberOfSubstrings(self, s: str) -> int:
        left = right = total = 0
        # Track frequency of a, b, c
        freq = [0] * 3

        while right < len(s):
            # Add character at right pointer to frequency array
            freq[ord(s[right]) - ord("a")] += 1

            # While we have all required characters
            while self._has_all_chars(freq):
                # All substrings from current window to end are valid
                # Add count of valid substrings
                print(f"{left}-{right}-{len(s) - right}")
                total += len(s) - right

                # Remove leftmost character and move left pointer
                freq[ord(s[left]) - ord("a")] -= 1
                left += 1

            right += 1

        return total

    def _has_all_chars(self, freq: list) -> bool:
        # Check if we have at least one of each character
        return all(f > 0 for f in freq)

class Solution2:
    def numberOfSubstrings(self, s: str) -> int:
        # Track last position of a, b, c
        last_pos = [-1] * 3
        total = 0

        for pos in range(len(s)):
            # Update last position of current character
            last_pos[ord(s[pos]) - ord("a")] = pos

            # Add count of valid substrings ending at current position
            # If any character is missing, min will be -1
            # Else min gives leftmost required character position
            total += 1 + min(last_pos)

        return total