diff --git a/README.md b/README.md
index 73ab537..ec7fd7a 100644
--- a/README.md
+++ b/README.md
@@ -34,7 +34,6 @@ Continually updated Python Notebooks containing TDD-based coding challenges and
| [unique_chars](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/unique_chars/unique_chars_solution.ipynb) | Determine if a string contains unique characters |
| [reverse_string](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_solution.ipynb) | Reverse characters in a string |
| [permutation](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/permutation/permutation_solution.ipynb) | Determine if a string is a permutation of another |
-| [replace_char](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/replace_char/replace_char_solution.ipynb) | Encode spaces in a string in-place |
| [compress](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/compress/compress_solution.ipynb) | Compress a string |
| [rotation](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/rotation/rotation_solution.ipynb) | Determine if a string is a rotation of another |
| [hash-map](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/hash_map/hash_map_solution.ipynb) | Implement a hash table with set, get, and remove methods |
diff --git a/arrays_strings/replace_char/__init__.py b/arrays_strings/replace_char/__init__.py
deleted file mode 100644
index e69de29..0000000
diff --git a/arrays_strings/replace_char/replace_char_challenge.ipynb b/arrays_strings/replace_char/replace_char_challenge.ipynb
deleted file mode 100644
index 77c60ab..0000000
--- a/arrays_strings/replace_char/replace_char_challenge.ipynb
+++ /dev/null
@@ -1,177 +0,0 @@
-{
- "cells": [
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "# Challenge Notebook"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Problem: Given a string (a list of characters), replace all spaces with '%20', in-place\n",
- "\n",
- "* [Constraints](#Constraints)\n",
- "* [Test Cases](#Test-Cases)\n",
- "* [Algorithm](#Algorithm)\n",
- "* [Code](#Code)\n",
- "* [Unit Test](#Unit-Test)\n",
- "* [Solution Notebook](#Solution-Notebook)"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Constraints\n",
- "\n",
- "*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
- "\n",
- "* Can we assume the string is ASCII?\n",
- " * Yes\n",
- " * Note: Unicode strings could require special handling depending on your language\n",
- "* Is there enough space in the data structure for this operation?\n",
- " * Yes\n",
- "* Since Python strings are immutable and we are asked to do this in-place, can I use a bytearray or a list instead?\n",
- " * Yes"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Test Cases\n",
- "\n",
- "* None -> None\n",
- "* ' ' -> '%20'\n",
- "* ' foo bar ' -> '%20foo%20bar%20'\n",
- "* 'foo' -> 'foo'"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Algorithm\n",
- "\n",
- "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/replace_char/replace_char_solution.ipynb). If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Code"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": null,
- "metadata": {
- "collapsed": false
- },
- "outputs": [],
- "source": [
- "def encode_spaces(string, length):\n",
- " # TODO: Implement me\n",
- " pass"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Unit Test"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "\n",
- "\n",
- "**The following unit test is expected to fail until you solve the challenge.**"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": null,
- "metadata": {
- "collapsed": false
- },
- "outputs": [],
- "source": [
- "# %load test_replace_char.py\n",
- "from nose.tools import assert_equal\n",
- "\n",
- "\n",
- "class TestReplace(object):\n",
- " \n",
- " def test_replace_char(self, func):\n",
- " # | are used to satisfy the constraint that\n",
- " # there is enough space in the string to\n",
- " # replace ' ' with '%20'\n",
- " # For each space, add two ||\n",
- " str0 = None\n",
- " str1 = bytearray(' ||')\n",
- " str2 = bytearray(' foo bar ||||||')\n",
- " str3 = bytearray('foo')\n",
- " func(str0, 0)\n",
- " func(str1, 1)\n",
- " func(str2, 9)\n",
- " func(str3, 3)\n",
- " assert_equal(str0, None)\n",
- " assert_equal(str1, '%20')\n",
- " assert_equal(str2, '%20foo%20bar%20')\n",
- " assert_equal(str3, 'foo')\n",
- " print('Success: test_replace_char')\n",
- "\n",
- "def main():\n",
- " test = TestReplace()\n",
- " test.test_replace_char(encode_spaces)\n",
- " \n",
- "if __name__ == '__main__':\n",
- " main()"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Solution Notebook\n",
- "\n",
- "Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/replace_char/replace_char_solution.ipynb) for a discussion on algorithms and code solutions."
- ]
- }
- ],
- "metadata": {
- "kernelspec": {
- "display_name": "Python 2",
- "language": "python",
- "name": "python2"
- },
- "language_info": {
- "codemirror_mode": {
- "name": "ipython",
- "version": 2
- },
- "file_extension": ".py",
- "mimetype": "text/x-python",
- "name": "python",
- "nbconvert_exporter": "python",
- "pygments_lexer": "ipython2",
- "version": "2.7.10"
- }
- },
- "nbformat": 4,
- "nbformat_minor": 0
-}
diff --git a/arrays_strings/replace_char/replace_char_solution.ipynb b/arrays_strings/replace_char/replace_char_solution.ipynb
deleted file mode 100644
index 7e6ca7c..0000000
--- a/arrays_strings/replace_char/replace_char_solution.ipynb
+++ /dev/null
@@ -1,240 +0,0 @@
-{
- "cells": [
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "# Solution Notebook"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Problem: Given a string (a list of characters), replace in-place all spaces with '%20'\n",
- "\n",
- "* [Constraints](#Constraints)\n",
- "* [Test Cases](#Test-Cases)\n",
- "* [Algorithm](#Algorithm)\n",
- "* [Code](#Code)\n",
- "* [Pythonic-Code: Not In-Place](#Pythonic-Code:-Not-In-Place)\n",
- "* [Unit Test](#Unit-Test)\n",
- "* [Solution Notebook](#Solution-Notebook)"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Constraints\n",
- "\n",
- "*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
- "\n",
- "* Can we assume the string is ASCII?\n",
- " * Yes\n",
- " * Note: Unicode strings could require special handling depending on your language\n",
- "* Is there enough space in the data structure for this operation?\n",
- " * Yes\n",
- "* Since Python strings are immutable and we are asked to do this in-place, can I use a list or a bytearray instead?\n",
- " * Yes"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Test Cases\n",
- "\n",
- "* None -> None\n",
- "* ' ' -> '%20'\n",
- "* ' foo bar ' -> '%20foo%20bar%20'\n",
- "* 'foo' -> 'foo'"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Algorithm\n",
- "\n",
- "Since Python strings are immutable, we'll use a bytearray instead to exercise in-place string manipulation as you would get with a C string.\n",
- "\n",
- "* Count the number of spaces in the bytearray\n",
- "* Determine the new bytearray length\n",
- "* For each character code in the bytearray, starting from the end of the string\n",
- " * If the character code is a space\n",
- " * bytearray[new length] = '0',\n",
- " * bytearray[new length - 1] = '2',\n",
- " * bytearray[new length - 2] = '%',\n",
- " * new length -= 3\n",
- " * Else\n",
- " * bytearray[new length] = character code,\n",
- " * new length -= 1\n",
- "\n",
- "Complexity:\n",
- "* Time: O(n)\n",
- "* Space: In-place"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Code"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 1,
- "metadata": {
- "collapsed": false
- },
- "outputs": [],
- "source": [
- "def encode_spaces(string, length):\n",
- " if string is None:\n",
- " return\n",
- " num_spaces = string.count(' ')\n",
- " new_length = length + 2 * num_spaces - 1\n",
- " for i in xrange(length-1, -1, -1):\n",
- " if chr(string[i]) == ' ':\n",
- " string[new_length] = '0'\n",
- " string[new_length-1] = '2'\n",
- " string[new_length-2] = '%'\n",
- " new_length -= 3\n",
- " else:\n",
- " string[new_length] = string[i]\n",
- " new_length -= 1"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Pythonic-Code: Not In-Place\n",
- "\n",
- "The following code is Pythonic, but requires using additional data structures as Python strings are immutable. You could use a bytearray or a list instead of a string to simulate manipulating an array of characters."
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 2,
- "metadata": {
- "collapsed": false
- },
- "outputs": [],
- "source": [
- "import re\n",
- "\n",
- "\n",
- "def encode_spaces_alt(string):\n",
- " return re.sub(' ', '%20', string)\n",
- "\n",
- "def encode_spaces_alt2(string):\n",
- " return string.replace(' ', '%20')"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## Unit Test"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 3,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "Overwriting test_replace_char.py\n"
- ]
- }
- ],
- "source": [
- "%%writefile test_replace_char.py\n",
- "from nose.tools import assert_equal\n",
- "\n",
- "\n",
- "class TestReplace(object):\n",
- " \n",
- " def test_replace_char(self, func):\n",
- " # | are used to satisfy the constraint that\n",
- " # there is enough space in the string to replace\n",
- " # ' ' with '%20'\n",
- " str0 = None\n",
- " str1 = bytearray(' ||')\n",
- " str2 = bytearray(' foo bar ||||||')\n",
- " str3 = bytearray('foo')\n",
- " func(str0, 0)\n",
- " func(str1, 1)\n",
- " func(str2, 9)\n",
- " func(str3, 3)\n",
- " assert_equal(str0, None)\n",
- " assert_equal(str1, '%20')\n",
- " assert_equal(str2, '%20foo%20bar%20')\n",
- " assert_equal(str3, 'foo')\n",
- " print('Success: test_replace_char')\n",
- "\n",
- "def main():\n",
- " test = TestReplace()\n",
- " test.test_replace_char(encode_spaces)\n",
- " \n",
- "if __name__ == '__main__':\n",
- " main()"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 4,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "Success: test_replace_char\n"
- ]
- }
- ],
- "source": [
- "run -i test_replace_char.py"
- ]
- }
- ],
- "metadata": {
- "kernelspec": {
- "display_name": "Python 2",
- "language": "python",
- "name": "python2"
- },
- "language_info": {
- "codemirror_mode": {
- "name": "ipython",
- "version": 2
- },
- "file_extension": ".py",
- "mimetype": "text/x-python",
- "name": "python",
- "nbconvert_exporter": "python",
- "pygments_lexer": "ipython2",
- "version": "2.7.10"
- }
- },
- "nbformat": 4,
- "nbformat_minor": 0
-}
diff --git a/arrays_strings/replace_char/test_replace_char.py b/arrays_strings/replace_char/test_replace_char.py
deleted file mode 100644
index 1d86f66..0000000
--- a/arrays_strings/replace_char/test_replace_char.py
+++ /dev/null
@@ -1,29 +0,0 @@
-from nose.tools import assert_equal
-
-
-class TestReplace(object):
-
- def test_replace_char(self, func):
- # | are used to satisfy the constraint that
- # there is enough space in the string to replace
- # ' ' with '%20'
- str0 = None
- str1 = bytearray(' ||')
- str2 = bytearray(' foo bar ||||||')
- str3 = bytearray('foo')
- func(str0, 0)
- func(str1, 1)
- func(str2, 9)
- func(str3, 3)
- assert_equal(str0, None)
- assert_equal(str1, '%20')
- assert_equal(str2, '%20foo%20bar%20')
- assert_equal(str3, 'foo')
- print('Success: test_replace_char')
-
-def main():
- test = TestReplace()
- test.test_replace_char(encode_spaces)
-
-if __name__ == '__main__':
- main()
\ No newline at end of file