Add 13th solution

solutions/13/13.ipynb

@@ -0,0 +1,195 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "id": "2338e70c-941e-47d1-b6c4-8f2cd1bd5685",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "#include <iostream>\n",
+    "#include <algorithm>\n",
+    "#include <cmath>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "783d966b-26f0-4074-a14e-73aaae3f4cce",
+   "metadata": {},
+   "source": [
+    "# Werte Tauschen"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "id": "af180c70-ab20-49bb-ae74-ed34fa3e9bfe",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "template<typename T>\n",
+    "void swap(T &a, T &b) {\n",
+    "    T tmp = a;\n",
+    "    a = b;\n",
+    "    b = a;\n",
+    "}"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "id": "fc50e18b-daf6-4e4f-8959-58395e3f1489",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "int a=1; int b=2;\n",
+    "swap(a,b);\n",
+    "assert(a==2);\n",
+    "assert(b==1);\n",
+    "std::string c=\"hallo\"; std::string d= \"welt\";\n",
+    "swap(c,d);\n",
+    "assert(c==\"welt\");\n",
+    "assert(d==\"hallo\");"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "71edb726-91b7-4d2e-bf88-48c454781b21",
+   "metadata": {},
+   "source": [
+    "# Werte sortieren"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "id": "8e188f82-b014-4949-a7bd-7d81dcecb846",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "template <typename T>\n",
+    "void sort_by_distance_to(std::vector<T> &vec, T distance_to) {\n",
+    "    std::sort(vec.begin(), vec.end(), [&] (const T &a, const T &b) -> bool {return std::abs(a - distance_to) < std::abs(b - distance_to);});\n",
+    "    return;\n",
+    "}"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "id": "548d66b4-f943-4048-b78c-780fc945dc3a",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "std::vector<int> test_vec {1,2,3,4,5,6}"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "id": "e4941422-785b-4895-8c2c-6b22276f93a8",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "sort_by_distance_to(test_vec, 5);"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "id": "fa6ab9b0-0d96-4bcb-ab77-4ad7a617fd74",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{ 5, 4, 6, 3, 2, 1 }"
+      ]
+     },
+     "execution_count": 7,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "test_vec"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "53e9fb64-b639-4f32-96f6-96dccc32d468",
+   "metadata": {
+    "tags": []
+   },
+   "source": [
+    "# Online Hilfe cppreference.com\n",
+    "1. \n",
+    "```c++\n",
+    "template< class ForwardIt, class T >\n",
+    "ForwardIt remove( ForwardIt first, ForwardIt last, const T& value );\n",
+    "```\n",
+    "2. `remove` removes all values matching the `value` parameter from the iterator given/bounded by `first` and `last` and returns the new end as a `ForwardIt`. To actually shrink the vector, [erase](https://en.cppreference.com/w/cpp/container/vector/erase) is used. This is called \"Erase–remove idiom\""
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "id": "45dea8c5-5ce2-4833-99f5-89d2be15c237",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "void remove_twos(std::vector<int> &vec) {\n",
+    "    auto it = std::remove(vec.begin(), vec.end(), 2);\n",
+    "    vec.erase(it, vec.end());\n",
+    "}"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 9,
+   "id": "9fcc99b4-0112-462e-8630-f8e7b6e95c2e",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{ 7, 3, 1, -5 }"
+      ]
+     },
+     "execution_count": 9,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "std::vector<int> numbers = {2,7,3,2,1,-5};\n",
+    "remove_twos(numbers);\n",
+    "numbers"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "44e725f3-50cc-4c8e-8e2c-f95f06e7eb4c",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "C++17",
+   "language": "C++17",
+   "name": "xcpp17"
+  },
+  "language_info": {
+   "codemirror_mode": "text/x-c++src",
+   "file_extension": ".cpp",
+   "mimetype": "text/x-c++src",
+   "name": "c++",
+   "version": "17"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}