Added an exercise on recursion.

Added lecture notes for lists and for loop.

4 files changed, 135 insertions, 0 deletions

diff --git a/python/problems/recursion/find_sum/common.py b/python/problems/recursion/find_sum/common.py
new file mode 100644
index 0000000..f61baa3
--- /dev/null
+++ b/python/problems/recursion/find_sum/common.py
@@ -0,0 +1,75 @@
+import re
+from python.util import has_token_sequence, string_almost_equal, \
+    string_contains_number, get_tokens, get_numbers, get_exception_desc, \
+    all_tokens, has_comprehension, has_loop, almost_equal, get_ast
+from server.hints import Hint
+
+id = 20809
+number = 9
+visible = True
+
+solution = '''\
+def find_sum(xs, gs):
+    if gs < 0:
+        return False
+    if gs == 0:
+        return True
+    if not xs:
+        return False
+    return find_sum(xs[1:], gs-xs[0]) or find_sum(xs[1:], gs)
+'''
+
+hint_type = {
+    'final_hint': Hint('final_hint')
+}
+
+def test(python, code, aux_code=''):
+    func_name = 'find_sum'
+    tokens = get_tokens(code)
+    if not has_token_sequence(tokens, ['def', func_name]):
+        return False, [{'id' : 'no_func_name', 'args' : {'func_name' : func_name}}]
+
+    in_out = [
+        (([2,7,3,1,4], 10), True),
+        (([2,3,2,4], 10), False),
+        (([], 10), False),
+        (([1,2,3], 2), True),
+        (([1,2,3], 7), False),
+        (([2,7,3,1,4], 9), True),
+        (([2,7,3,2,4], 17), False),
+    ]
+
+    test_in = [('{0}{1}'.format(func_name, str(l[0])), None)
+               for l in in_out]
+    test_out = [l[1] for l in in_out]
+
+    answers = python(code=aux_code+code, inputs=test_in, timeout=1.0)
+    n_correct = 0
+    tin, tout = None, None
+    for i, (ans, to) in enumerate(zip(answers, test_out)):
+        res = ans[0]
+        corr = res == to
+        n_correct += corr
+        if not corr:
+            tin = test_in[i][0]
+            tout = to
+
+    passed = n_correct == len(test_in)
+    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_in)}}]
+    if tin:
+        hints.append({'id': 'problematic_test_case', 'args': {'testin': str(tin), 'testout': str(tout)}})
+    if passed:
+        hints.append({'id': 'final_hint'})
+
+    return passed, hints
+
+
+def hint(python, code, aux_code=''):
+    tokens = get_tokens(code)
+
+    # run one test first to see if there are any exceptions
+    answer = python(code=aux_code+code, inputs=[(None, None)], timeout=1.0)
+    exc = get_exception_desc(answer[0][3])
+    if exc: return exc
+
+    return None
diff --git a/python/problems/recursion/find_sum/en.py b/python/problems/recursion/find_sum/en.py
new file mode 100644
index 0000000..0d1807c
--- /dev/null
+++ b/python/problems/recursion/find_sum/en.py
@@ -0,0 +1,13 @@
+id = 20809
+name = 'Find sum'
+
+description = '''\
+<p>(translation missing)</p>'''
+
+hint = {
+    'plan': '''\
+<p>(translation missing)</p>''',
+
+    'no_input_call': '''\
+<p>(translation missing)</p>''',
+}
diff --git a/python/problems/recursion/find_sum/find_sum.py b/python/problems/recursion/find_sum/find_sum.py
new file mode 100644
index 0000000..85f472b
--- /dev/null
+++ b/python/problems/recursion/find_sum/find_sum.py
@@ -0,0 +1,19 @@
+def find_sum(xs, gs):
+    if gs < 0:
+        return False
+    if gs == 0:
+        return True
+    if not xs:
+        return False
+    return find_sum(xs[1:], gs-xs[0]) or find_sum(xs[1:], gs)
+
+print (find_sum([2,7,3,1,4], 10))
+print (find_sum([2,3,2,4], 10))
+print (find_sum([], 10))
+print (find_sum([1,2,3], 2))
+print (find_sum([1,2,3], 7))
+print (find_sum([2,7,3,1,4], 9))
+print (find_sum([2,7,3,2,4], 17))
+
+
+
diff --git a/python/problems/recursion/find_sum/sl.py b/python/problems/recursion/find_sum/sl.py
new file mode 100644
index 0000000..00aad43
--- /dev/null
+++ b/python/problems/recursion/find_sum/sl.py
@@ -0,0 +1,28 @@
+import server
+mod = server.problems.load_language('python', 'sl')
+
+id = 20809
+name = 'Išči vsoto'
+
+description = '''\
+<p>
+Napiši funkcijo <code>find_sum(xs, gs)</code>, ki kot argument prejme seznam
+pozitivnih števil in število, ki predstavlja ciljno vsoto. Funkcija vrne
+<code>True</code>, kadar lahko sestavimo ciljno vsoto iz števil v seznamu. </p>
+
+<pre>
+>>> find_sum([2,7,3,1,4], 10)
+True
+>>> find_sum([2,3,2,4], 10)
+False
+</pre>
+'''
+
+plan = []
+
+hint = {
+    'final_hint': ['''\
+<p>Program je pravilen! <br>
+</p>
+''']
+}