Fix binary search to return first occurrence for duplicates

### Fix: Binary Search Incorrect Output for Duplicates

Previously, the binary_search function returned any matching index when duplicates were present.

This change modifies the implementation to return the **first occurrence** of the target element.

### Changes made:
- Introduced a `result` variable to track the first occurrence
- Continued searching in the left half after finding a match
- Updated final return to return `result` instead of immediate index

### Example:
Input: [1, 2, 2, 2, 3], target = 2  
Output (before): could be 1, 2, or 3  
Output (after): 1 (first occurrence)

This resolves issue: #13840

Author: Pranavwagh1

searches/binary_search.py

@@ -202,17 +202,18 @@ def binary_search(sorted_collection: list[int], item: int) -> int:
         raise ValueError("sorted_collection must be sorted in ascending order")
     left = 0
     right = len(sorted_collection) - 1
-
+    result = -1 
     while left <= right:
         midpoint = left + (right - left) // 2
         current_item = sorted_collection[midpoint]
         if current_item == item:
-            return midpoint
+            result = midpoint
+            right = midpoint - 1
         elif item < current_item:
             right = midpoint - 1
         else:
             left = midpoint + 1
-    return -1
+    return result 
 
 
 def binary_search_std_lib(sorted_collection: list[int], item: int) -> int: