add three algo in the array section

Author: Sangram03

data_structures/arrays/majority_element.py

@@ -0,0 +1,35 @@
+"""
+Find the majority element in an array.
+"""
+
+def majority_element(nums: list[int]) -> int:
+    """
+    Find the element that appears more than n/2 times using
+    Boyer-Moore Voting Algorithm.
+
+    Args:
+        nums: List of integers.
+
+    Returns:
+        The majority element.
+
+    Examples:
+        >>> majority_element([3, 2, 3])
+        3
+        >>> majority_element([2, 2, 1, 1, 1, 2, 2])
+        2
+    """
+    count = 0
+    candidate = None
+
+    for num in nums:
+        if count == 0:
+            candidate = num
+        count += (1 if num == candidate else -1)
+
+    return candidate
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()

data_structures/arrays/maximum_subarray.py

@@ -0,0 +1,34 @@
+"""
+Find the maximum subarray sum (Kadane's Algorithm).
+"""
+
+def max_subarray(nums: list[int]) -> int:
+    """
+    Find the contiguous subarray with the largest sum.
+
+    Args:
+        nums: List of integers.
+
+    Returns:
+        Maximum sum of subarray.
+
+    Examples:
+        >>> max_subarray([-2,1,-3,4,-1,2,1,-5,4])
+        6
+        >>> max_subarray([1])
+        1
+        >>> max_subarray([5,4,-1,7,8])
+        23
+    """
+    max_sum = current_sum = nums[0]
+
+    for num in nums[1:]:
+        current_sum = max(num, current_sum + num)
+        max_sum = max(max_sum, current_sum)
+
+    return max_sum
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()

data_structures/arrays/rotate_array.py

@@ -0,0 +1,31 @@
+"""
+Rotate an array to the right by k steps.
+"""
+
+def rotate(nums: list[int], k: int) -> list[int]:
+    """
+    Rotate the array to the right by k steps.
+
+    Args:
+        nums: List of integers.
+        k: Number of steps to rotate.
+
+    Returns:
+        The rotated list.
+
+    Examples:
+        >>> rotate([1,2,3,4,5,6,7], 3)
+        [5, 6, 7, 1, 2, 3, 4]
+
+        >>> rotate([-1,-100,3,99], 2)
+        [3, 99, -1, -100]
+    """
+    n = len(nums)
+    k = k % n  # In case k > n
+    nums[:] = nums[-k:] + nums[:-k]
+    return nums
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()