adding updates

src/my_project/interviews/amazon_high_frequency_23/round_7/number_of_ways_to_select_building.py

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+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution:
+    def numberOfWays(self, s: str) -> int:
+        """
+        Count valid 3-building selections forming "010" or "101" patterns.
+
+        Key insight: Track how many 2-character patterns we can form,
+        then extend them with the appropriate third character.
+
+        Time: O(n), Space: O(1)
+        """        
+        total_zeros = s.count('0')
+        total_ones = len(s) - total_zeros
+
+        left_zeros = left_ones = 0
+        ways = 0
+
+        for ch in s:
+            if ch == '1':
+                # middle is '1' -> need '0' on both sides -> "010"
+                right_zeros = total_zeros - left_zeros
+                ways += left_zeros * right_zeros
+                left_ones += 1
+            else:  # ch == '0'
+                # middle is '0' -> need '1' on both sides -> "101"
+                right_ones = total_ones - left_ones
+                ways += left_ones * right_ones
+                left_zeros += 1
+
+        return ways