Polish fibonacci challenge and solution (#91)

Update constraints, test cases, tests, and code.

recursion_dynamic/fibonacci/fibonacci_challenge.ipynb

@@ -34,7 +34,14 @@
    "source": [
     "## Constraints\n",
     "\n",
-    "* None"
+    "* Does the sequence start at 0 or 1?\n",
+    "    * 0\n",
+    "* Can we assume the inputs are valid non-negative ints?\n",
+    "    * Yes\n",
+    "* Are you looking for a recursive or iterative solution?\n",
+    "    * Implement both\n",
+    "* Can we assume this fits memory?\n",
+    "    * Yes"
    ]
   },
   {
@@ -45,7 +52,8 @@
     "\n",
     "* n = 0 -> 0\n",
     "* n = 1 -> 1\n",
-    "* n > 1 -> 0, 1, 1, 2, 3, 5, 8, 13, 21, 34..."
+    "* n = 6 -> 8\n",
+    "* Fib sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34..."
    ]
   },
   {
@@ -85,11 +93,7 @@
    },
    "outputs": [],
    "source": [
-    "num_items = 10\n",
+    "def fib_iterative(n):\n",
-    "cache = [None] * (num_items + 1)\n",
-    "\n",
-    "\n",
-    "def fib_dynamic(n):\n",
     "    # TODO: Implement me\n",
     "    pass"
    ]
@@ -102,7 +106,7 @@
    },
    "outputs": [],
    "source": [
-    "def fib_iterative(n):\n",
+    "def fib_dynamic(n):\n",
     "    # TODO: Implement me\n",
     "    pass"
    ]
@@ -134,10 +138,10 @@
     "\n",
     "    def test_fib(self, func):\n",
     "        result = []\n",
-    "        for i in range(num_items):\n",
+    "        expected = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]\n",
+    "        for i in range(len(expected)):\n",
     "            result.append(func(i))\n",
-    "        fib_seq = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]\n",
+    "        assert_equal(result, expected)\n",
-    "        assert_equal(result, fib_seq)\n",
     "        print('Success: test_fib')\n",
     "\n",
     "\n",
@@ -164,21 +168,21 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 2",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "python2"
+   "name": "python3"
   },
   "language_info": {
    "codemirror_mode": {
     "name": "ipython",
-    "version": 2
+    "version": 3
    },
    "file_extension": ".py",
    "mimetype": "text/x-python",
    "name": "python",
    "nbconvert_exporter": "python",
-   "pygments_lexer": "ipython2",
+   "pygments_lexer": "ipython3",
-   "version": "2.7.10"
+   "version": "3.5.0"
   }
  },
  "nbformat": 4,

recursion_dynamic/fibonacci/fibonacci_solution.ipynb

@@ -33,7 +33,14 @@
    "source": [
     "## Constraints\n",
     "\n",
-    "* None"
+    "* Does the sequence start at 0 or 1?\n",
+    "    * 0\n",
+    "* Can we assume the inputs are valid non-negative ints?\n",
+    "    * Yes\n",
+    "* Are you looking for a recursive or iterative solution?\n",
+    "    * Either\n",
+    "* Can we assume this fits memory?\n",
+    "    * Yes"
    ]
   },
   {
@@ -44,7 +51,8 @@
     "\n",
     "* n = 0 -> 0\n",
     "* n = 1 -> 1\n",
-    "* n > 1 -> 0, 1, 1, 2, 3, 5, 8, 13, 21, 34..."
+    "* n = 6 -> 8\n",
+    "* Fib sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34..."
    ]
   },
   {
@@ -93,17 +101,12 @@
    },
    "outputs": [],
    "source": [
-    "num_items = 10\n",
+    "def fib_iterative(n):\n",
-    "cache = [None] * (num_items + 1)\n",
+    "    a = 0\n",
-    "\n",
+    "    b = 1\n",
-    "\n",
+    "    for _ in range(n):\n",
-    "def fib_dynamic(n):\n",
+    "        a, b = b, a + b\n",
-    "    if n == 0 or n == 1:\n",
+    "    return a"
-    "        return n\n",
-    "    if cache[n] != None:\n",
-    "        return cache[n]\n",
-    "    cache[n] = fib_dynamic(n-1) + fib_dynamic(n-2)\n",
-    "    return cache[n]"
    ]
   },
   {
@@ -114,12 +117,18 @@
    },
    "outputs": [],
    "source": [
-    "def fib_iterative(n):\n",
+    "def fib_dynamic(n):\n",
-    "    a = 0\n",
+    "    cache = {}\n",
-    "    b = 1\n",
+    "    return _fib_dynamic(n, cache)\n",
-    "    for _ in range(n):\n",
+    "\n",
-    "        a, b = b, a + b\n",
+    "\n",
-    "    return a"
+    "def _fib_dynamic(n, cache):\n",
+    "    if n == 0 or n == 1:\n",
+    "        return n\n",
+    "    if n in cache:\n",
+    "        return cache[n]\n",
+    "    cache[n] = _fib_dynamic(n-1, cache) + _fib_dynamic(n-2, cache)\n",
+    "    return cache[n]"
    ]
   },
   {
@@ -154,10 +163,10 @@
     "\n",
     "    def test_fib(self, func):\n",
     "        result = []\n",
-    "        for i in range(num_items):\n",
+    "        expected = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]\n",
+    "        for i in range(len(expected)):\n",
     "            result.append(func(i))\n",
-    "        fib_seq = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]\n",
+    "        assert_equal(result, expected)\n",
-    "        assert_equal(result, fib_seq)\n",
     "        print('Success: test_fib')\n",
     "\n",
     "\n",
@@ -196,21 +205,21 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 2",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "python2"
+   "name": "python3"
   },
   "language_info": {
    "codemirror_mode": {
     "name": "ipython",
-    "version": 2
+    "version": 3
    },
    "file_extension": ".py",
    "mimetype": "text/x-python",
    "name": "python",
    "nbconvert_exporter": "python",
-   "pygments_lexer": "ipython2",
+   "pygments_lexer": "ipython3",
-   "version": "2.7.10"
+   "version": "3.5.0"
   }
  },
  "nbformat": 4,

recursion_dynamic/fibonacci/test_fibonacci.py

@@ -5,10 +5,10 @@ class TestFib(object):
 
     def test_fib(self, func):
         result = []
-        for i in range(num_items):
+        expected = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
+        for i in range(len(expected)):
             result.append(func(i))
-        fib_seq = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
+        assert_equal(result, expected)
-        assert_equal(result, fib_seq)
         print('Success: test_fib')