Cleaned up string compress notebook. Refactored duplicate algorithm description.

arrays-strings/compress.ipynb

@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Compress a String Such that 'AAABCCDDDD' Becomes 'A3B1C2D4'.  Only Compress if it Saves Space.\n",
+    "## Problem: Compress a string such that 'AAABCCDDDD' becomes 'A3B1C2D4'\n",
     "\n",
     "* [Clarifying Questions](#Clarifying-Questions)\n",
     "* [Test Cases](#Test-Cases)\n",
@@ -25,7 +25,9 @@
     "* Can you use additional data structures?  \n",
     "    * Yes\n",
     "* Is this case sensitive?\n",
-    "    * Yes"
+    "    * Yes\n",
+    "* Do you compress even if it doesn't save space?\n",
+    "    * No"
    ]
   },
   {
@@ -48,7 +50,7 @@
     "\n",
     "![alt text](https://raw.githubusercontent.com/donnemartin/algorithms-data-structures/master/images/compress_string.jpg)\n",
     "\n",
-    "Since Python strings are immutable, we'll use a list to exercise array manipulation.  Note using a list vs a bytearray will will result in additional space to create the list and to convert the list to a string.\n",
+    "Since Python strings are immutable, we'll use a list of characters to exercise string manipulation.  Note using a list vs a bytearray will will result in additional space to create the list and to convert the list to a string.\n",
     "\n",
     "* If string is empty return string\n",
     "* count = 0\n",
@@ -78,7 +80,7 @@
     "\n",
     "Complexity:\n",
     "* Time: O(n)\n",
-    "* Space: O(m) where m is the size of the compressed bytearray"
+    "* Space: O(2m) where m is the size of the compressed list and the resulting string copied from the list"
    ]
   },
   {
@@ -145,35 +147,9 @@
     "\n",
     "![alt text](https://raw.githubusercontent.com/donnemartin/algorithms-data-structures/master/images/compress_string.jpg)\n",
     "\n",
-    "Since Python strings are immutable, we'll use a bytearray to exercise array manipulation.  We could use a list of characters to create the compressed string then convert it to a string in the end, but this will result in additional space.\n",
+    "Since Python strings are immutable, we'll use a bytearray to exercise array manipulation.  As seen above, we could use a list of characters to create the compressed string then convert it to a string in the end, but this will result in additional space.\n",
     "\n",
-    "* If bytearray is empty return bytearray\n",
+    "The algorithm is the same, except we will need to work with the bytearray's character codes instead of the characters as we did above when we implemented this solution with a list.\n",
-    "* count = 0\n",
-    "* size = 0\n",
-    "* last_char_code = first char code in bytearray\n",
-    "* For each char code in bytearray\n",
-    "    * If char code == last_char_code\n",
-    "        count++\n",
-    "    * Else\n",
-    "        size += 2\n",
-    "        count++\n",
-    "        last_char_code = char code\n",
-    "* size += 2\n",
-    "* If the compressed bytearray size is >= bytearray size, return string\n",
-    "* Create compressed_bytearray\n",
-    "* pos = 0\n",
-    "* For each char code in bytearray\n",
-    "    * If char code == last_char_code\n",
-    "        count++\n",
-    "    * Else\n",
-    "        * compressed_bytearray[pos] = last_char_code\n",
-    "        * compressed_bytearray[pos + 1] = count\n",
-    "        * pos += 2\n",
-    "        * count = 1\n",
-    "        * last_char_code = char code\n",
-    "    * compressed_bytearray[pos] = last_char_code\n",
-    "    * compressed_bytearray[pos + 1] = count\n",
-    "* return compressed_bytearray\n",
     "\n",
     "Complexity:\n",
     "* Time: O(n)\n",