added kadane's algo

data_structures/arrays/kadanes_algorithm.py

@@ -0,0 +1,42 @@
+# Kadane's algorithm
+
+
+def kadanes_algorithm(arr: list[int]) -> int:
+    """
+    Function to find the maximum sum of a contiguous subarray using Kadane's algorithm
+
+    >>> kadanes_algorithm([-2, 1, -3, 4, -1, 2, 1, -5, 4])
+    6
+
+    >>> kadanes_algorithm([-1, -2, -3, -4])
+    -1
+
+    >>> kadanes_algorithm([5, 4, -1, 7, 8])
+    23
+
+    >>> kadanes_algorithm([1])
+    1
+
+    >>> kadanes_algorithm([-1, 2, 3, -5, 4])
+    5
+    """
+    # initializing variables
+    max_current = arr[0]  # store the current max sum
+    max_global = arr[0]  # store the global max sum
+
+    # looping through the array starting at the second element
+    for i in range(1, len(arr)):
+        # update current max sum by choosing the maximum between
+        # current element alone or current element plus previous max
+        max_current = max(arr[i], max_current + arr[i])
+
+        # update global max sum if current max is larger
+        max_global = max(max_current, max_global)
+
+    return max_global
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()