Implement Kadane's Algorithm to find Maximum Subarray Sum (Issue #7)

python/maximum-subarray-sum.py

@@ -0,0 +1,48 @@
+# Function finds the largest sum of any contiguous subarray using Kadane's algorithm
+# Input: list of numbers
+# Output: int
+# Runtime Complexity: O(n), Space Complexcity: O(1)
+def max_subarray_sum(numbers: list[int]) -> int:
+    if len(numbers) == 0:
+        raise(ValueError("Empty array provided"))
+    best_sum = float('-inf')
+    current_sum = 0
+    for x in numbers:
+        current_sum = max(x, current_sum + x)
+        best_sum = max(best_sum, current_sum)
+    return best_sum
+
+def test(input=[-2, 1, -3, 4, -1, 2, 1, -5, 4]): # Default value
+    output = max_subarray_sum(input)
+    print(f"Input: {input} => Maximum subarray sum: {output}")
+
+def sample1():
+    """
+    Input: [-2, 1, -3, 4, -1, 2, 1, -5, 4]
+    Output: Maximum subarray sum is 6
+    Explanation: [4, -1, 2, 1] has the largest sum = 6
+    """
+    test([-2, 1, -3, 4, -1, 2, 1, -5, 4])
+
+
+def sample2():
+    """
+    Input: [-1, -2, -1]
+    Output: Maximum subarray sum is -1
+    Explanation: [-1] has the largest sum = -1
+    """
+    test([-1, -2, -1])
+
+def sample3():
+    """
+    Input: [1, 2, -3, 4, 5]
+    Output: Maximum subarray sum is 9
+    Explanation: [4, 5] has the largest sum = 9
+    """
+    test([1, 2, -3, 4, 5])
+
+if __name__ == "__main__":
+    #sample1()
+    #sample2()
+    #sample3()
+    pass