added algorithm to find majority element in the array using the boyer-moore algorithm

Author: arvinder004

data_structures/arrays/majority_element.py

@@ -0,0 +1,42 @@
+def majority_element(arr: list[int]) -> int | None:
+    """
+    Find the majority element in an array using the Boyer-Moore Voting Algorithm
+    The majority element is the element that appears more than n/2 times (n is the size of the array)
+
+    Args:
+        arr(list[int]): The input array
+    
+    Returns:
+        int | None: The majority element if it exists
+    
+    Examples:
+        >>> majority_element([3, 3, 4, 2, 4, 4, 2, 4, 4])
+        4
+        >>> majority_element([2, 2, 1, 1, 1, 2, 2])
+        2
+        >>> majority_element([1, 2, 3])
+        None
+        >>> majority_element([])
+        None
+    """
+
+    count = 0
+    majority = None
+
+    for num in arr:
+        if count == 0:
+            majority = num
+            count = 1
+        elif num == majority:
+            count += 1
+        else:
+            count -= 1
+    
+    if majority is not None and arr.count(majority) > len(arr) // 2:
+        return majority
+    return None
+
+
+if __name__ == "__main__":
+    arr = [3, 3, 4, 2, 4, 4, 2, 4, 4]
+    print("Majority element: ", majority_element(arr))