Data commit

Task/Greatest-subsequential-sum/Python/greatest-subsequential-sum-1.py

@@ -0,0 +1,4 @@
+def maxsubseq(seq):
+  return max((seq[begin:end] for begin in xrange(len(seq)+1)
+                             for end in xrange(begin, len(seq)+1)),
+             key=sum)

Task/Greatest-subsequential-sum/Python/greatest-subsequential-sum-2.py

@@ -0,0 +1,8 @@
+def maxsum(sequence):
+    """Return maximum sum."""
+    maxsofar, maxendinghere = 0, 0
+    for x in sequence:
+        # invariant: ``maxendinghere`` and ``maxsofar`` are accurate for ``x[0..i-1]``
+        maxendinghere = max(maxendinghere + x, 0)
+        maxsofar = max(maxsofar, maxendinghere)
+    return maxsofar

Task/Greatest-subsequential-sum/Python/greatest-subsequential-sum-3.py

@@ -0,0 +1,14 @@
+def maxsumseq(sequence):
+    start, end, sum_start = -1, -1, -1
+    maxsum_, sum_ = 0, 0
+    for i, x in enumerate(sequence):
+        sum_ += x
+        if maxsum_ < sum_: # found maximal subsequence so far
+            maxsum_ = sum_
+            start, end = sum_start, i
+        elif sum_ < 0: # start new sequence
+            sum_ = 0
+            sum_start = i
+    assert maxsum_ == maxsum(sequence)
+    assert maxsum_ == sum(sequence[start + 1:end + 1])
+    return sequence[start + 1:end + 1]

Task/Greatest-subsequential-sum/Python/greatest-subsequential-sum-4.py

@@ -0,0 +1,14 @@
+def maxsumit(iterable):
+    maxseq = seq = []
+    start, end, sum_start = -1, -1, -1
+    maxsum_, sum_ = 0, 0
+    for i, x in enumerate(iterable):
+        seq.append(x); sum_ += x
+        if maxsum_ < sum_:
+            maxseq = seq; maxsum_ = sum_
+            start, end = sum_start, i
+        elif sum_ < 0:
+            seq = []; sum_ = 0
+            sum_start = i
+    assert maxsum_ == sum(maxseq[:end - start])
+    return maxseq[:end - start]

Task/Greatest-subsequential-sum/Python/greatest-subsequential-sum-5.py

@@ -0,0 +1,17 @@
+f = maxsumit
+assert f([]) == []
+assert f([-1]) == []
+assert f([0])  == []
+assert f([1])       == [1]
+assert f([1, 0])    == [1]
+assert f([0, 1])    == [0, 1]
+assert f([0, 1, 0]) == [0, 1]
+assert f([2])         == [2]
+assert f([2, -1])     == [2]
+assert f([-1, 2])     == [2]
+assert f([-1, 2, -1]) == [2]
+assert f([2, -1, 3])         == [2, -1, 3]
+assert f([2, -1, 3, -1])     == [2, -1, 3]
+assert f([-1, 2, -1, 3])     == [2, -1, 3]
+assert f([-1, 2, -1, 3, -1]) == [2, -1, 3]
+assert f([-1, 1, 2, -5, -6]) == [1,2]

Task/Greatest-subsequential-sum/Python/greatest-subsequential-sum-6.py

@@ -0,0 +1,21 @@
+'''Greatest subsequential sum'''
+
+from functools import (reduce)
+
+
+# maxSubseq :: [Int] -> [Int] -> (Int, [Int])
+def maxSubseq(xs):
+    '''Subsequence of xs with the maximum sum'''
+    def go(ab, x):
+        (m1, m2) = ab[0]
+        hi = max((0, []), (m1 + x, m2 + [x]))
+        return (hi, max(ab[1], hi))
+    return reduce(go, xs, ((0, []), (0, [])))[1]
+
+
+# TEST -----------------------------------------------------------
+print(
+    maxSubseq(
+        [-1, -2, 3, 5, 6, -2, -1, 4, -4, 2, -1]
+    )
+)