Kadane's algorithm for maximum sum contiguous subarray

allalgorithms/subarray/__init__.py

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+from .kadane import *

allalgorithms/subarray/kadane.py

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+# -*- coding: UTF-8 -*-
+#
+# Kadane's Algorithm
+# The All ▲lgorithms library for python
+#
+# Contributed by: Kunal Keshav Singh Sahni 
+# Github: @kunal768
+#
+
+import sys
+
+def maxsum_subarray(arr):
+	curr = arr[0]
+	maxx = arr[0]
+	n = len(arr)
+
+	for i in range(1,n):
+		curr = max(arr[i],curr+arr[i])
+		maxx = max(curr,maxx)
+
+	return maxx
+
+
+def returnArray(arr):
+    size = len(arr) 
+    max_so_far = -sys.maxsize - 1
+    max_ending_here = 0
+    start = 0
+    end = 0
+    s = 0
+    for i in range(0,size): 
+
+        max_ending_here += arr[i] 
+
+        if max_so_far < max_ending_here: 
+            max_so_far = max_ending_here 
+            start = s 
+            end = i 
+
+        if max_ending_here < 0: 
+            max_ending_here = 0
+            s = i+1
+
+    return [max_so_far,arr[start:end+1]]

docs/readme.md

@@ -69,10 +69,15 @@ print(binary_search(arr, 3))
   - [Merge Sort](https://python.allalgorithms.com/sorting/merge-sort)
   - [Pigeonhole Sort](https://python.allalgorithms.com/sorting/pigeonhole-sort)
   - [Selection Sort](https://python.allalgorithms.com/sorting/selection-sort)
-  - [Stooge Sort](https://python.allalgorithms.com/sorting/stooge-sort)
+  - [Stooge Sort](https://python.allalgorithms.com/sorting/stooge-sor
+
 - ### String
   - [Palindrome Check](https://python.allalgorithms.com/string/palindrom-check)
 
+- ### Subarray
+  - [Kadane's Algorithm](https://github.com/kunal768/allalgorithms-python/blob/master/allalgorithms/subarray/kadane.py)
+
+
 # Related
 
 - [allalgorithms-javascript](https://github.com/abranhe/allalgorithms-javascript): All ▲lgorithms Javascript library

docs/subarray/kadane.md

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+# Kadane's Algorithm 
+
+Kadane’s algorithm is to look for all positive contiguous segments of the array (max_ending_here is used for this). And keep track of maximum sum contiguous segment among all positive segments (max_so_far is used for this) Each time we get a positive sum compare it with max_so_far and update max_so_far if it is greater than max_so_far
+## Install
+
+```
+pip install allalgorithms
+```
+
+## Usage
+
+```py
+from allalgorithms.subarray import kadane
+
+arr = [-2, 1, 2, 7, 10, 77]
+
+print(kadane.maxsum_subarray(arr))
+# -> 97
+
+print(kadane.returnArray(arr))
+# -> [97, [1, 2, 7, 10, 77]]
+```
+
+## API
+
+### maxsum_subarray(array)
+
+> Return sum of maximum contigious subarray
+
+### returnArray(array)
+
+> Return sum along with the respective subarray
+
+##### Params:
+
+- `array`: Array (may contain negative elements)

readme.md

@@ -70,9 +70,14 @@ print(binary_search(arr, 3))
   - [Pigeonhole Sort](https://python.allalgorithms.com/sorting/pigeonhole-sort)
   - [Selection Sort](https://python.allalgorithms.com/sorting/selection-sort)
   - [Stooge Sort](https://python.allalgorithms.com/sorting/stooge-sort)
+
 - ### String
   - [Palindrome Check](https://python.allalgorithms.com/string/palindrom-check)
 
+- ### Subarray
+  - [Kadane's Algorithm](https://python.allalgorithms.com/subarray/kadane)
+
+
 # Related
 
 - [allalgorithms-javascript](https://github.com/abranhe/allalgorithms-javascript): All ▲lgorithms Javascript library

tests/test_kadane.py

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+import unittest
+
+from allalgorithms.subarray import kadane
+
+class TestSearches(unittest.TestCase):
+	def test_returnArray(self):
+		self.assertEqual( [11,[2,3,-1,7]], kadane.returnArray([2,3,-1,7]))
+		self.assertEqual([5,[2,3]], kadane.returnArray([2,3,-2,4]))
+		self.assertEqual([0, [0]], kadane.returnArray([-1,-1,-0,0]))
+		self.assertEqual([-1, [-1]], kadane.returnArray([-1]))
+
+	def test_maxsum_subarray(self):
+		self.assertEqual(11,kadane.maxsum_subarray([2,3,-1,7]))
+		self.assertEqual(5, kadane.maxsum_subarray([2,3,-2,4]))
+		self.assertEqual(0, kadane.maxsum_subarray([-1,-1,-0,0]))
+		self.assertEqual(-1, kadane.maxsum_subarray([-1]))
+
+if __name__ == '__main__':
+	unittest.main()