Adding tests for max subseq. Now this will break.

skytreader · Mar 24, 2016 · 576d1dc · 576d1dc
1 parent 9a153ed
commit 576d1dc
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Showing 2 changed files with 28 additions and 6 deletions.
diff --git a/algorithms/max_subseq.py b/algorithms/max_subseq.py
@@ -116,19 +116,28 @@ def max_subarray(numseq):
     return find_max_subarray(numseq, 0, len(numseq) - 1)
 
 def max_subarray_dp(numseq):
+    """
+    Returns a tuple containing the start index of the max subarray, the end
+    index of the max subarray, and the sum over that subarray, in that order.
+    """
     maxjs = []
-    max_idxs = []
+    max_ends = []
+    max_starts = []
+
     for idx, val in enumerate(numseq):
         if idx != 0:
             cont = maxjs[idx - 1] + numseq[idx]
             if cont > numseq[idx]:
                 maxjs.append(cont)
-                max_idxs.append(maxj_idxs[idx - 1])
+                max_ends.append(idx)
+                max_starts.append(max_starts[idx - 1])
             else:
                 maxjs.append(numseq[idx])
-                max_idxs.append(idx)
+                max_ends.append(idx)
+                max_starts.append(idx)
         else:
             maxjs.append(numseq[0])
-            max_idxs.append(0)
+            max_ends.append(0)
+            max_starts.append(0)
 
-    return (maxjs[-1], max_idxs[-1])
+    return (max_starts[-1], max_ends[-1], maxjs[-1])
diff --git a/algorithms/tests/max_subseq_tests.py b/algorithms/tests/max_subseq_tests.py
@@ -1,4 +1,4 @@
-from ..max_subseq import max_subarray, find_biased_max
+from ..max_subseq import max_subarray, max_subarray_dp, find_biased_max
 
 import unittest
 
@@ -19,3 +19,16 @@ def test_max_subarray(self):
         self.assertEqual((1, 2, 50), max_subarray((-5, 40, 10)))
         self.assertEqual((0, 0, -10), max_subarray([-10]))
         self.assertEqual((3, 6, 55), max_subarray((5, 15, -30, 10, -5, 40, 10)))
+
+    def test_max_subarray_dp(self):
+        self.assertEqual((0, 1, 20), max_subarray((5, 15, -30, 10)))
+        # The example from the book
+        stocks = [13, -3, -25, 20, -3, -16, -23, 18, 20, -7, 12, -5, -22, 15, -4, 7]
+        self.assertEqual((7, 10, 43), max_subarray_dp(stocks))
+        self.assertEqual((0, 1, 10), max_subarray_dp((7, 3)))
+        self.assertEqual((1, 1, 10), max_subarray_dp((-10, 10)))
+        self.assertEqual((0, 0, 10), max_subarray_dp((10, -10)))
+        self.assertEqual((0, 0, 10), max_subarray_dp([10]))
+        self.assertEqual((1, 2, 50), max_subarray_dp((-5, 40, 10)))
+        self.assertEqual((0, 0, -10), max_subarray_dp([-10]))
+        self.assertEqual((3, 6, 55), max_subarray_dp((5, 15, -30, 10, -5, 40, 10)))