"content":"<p>An underground railway system is keeping track of customer travel times between different stations. They are using this data to calculate the average time it takes to travel from one station to another.</p>\n\n<p>Implement the <code>UndergroundSystem</code> class:</p>\n\n<ul>\n\t<li><code>void checkIn(int id, string stationName, int t)</code>\n\n\t<ul>\n\t\t<li>A customer with a card ID equal to <code>id</code>, checks in at the station <code>stationName</code> at time <code>t</code>.</li>\n\t\t<li>A customer can only be checked into one place at a time.</li>\n\t</ul>\n\t</li>\n\t<li><code>void checkOut(int id, string stationName, int t)</code>\n\t<ul>\n\t\t<li>A customer with a card ID equal to <code>id</code>, checks out from the station <code>stationName</code> at time <code>t</code>.</li>\n\t</ul>\n\t</li>\n\t<li><code>double getAverageTime(string startStation, string endStation)</code>\n\t<ul>\n\t\t<li>Returns the average time it takes to travel from <code>startStation</code> to <code>endStation</code>.</li>\n\t\t<li>The average time is computed from all the previous traveling times from <code>startStation</code> to <code>endStation</code> that happened <strong>directly</strong>, meaning a check in at <code>startStation</code> followed by a check out from <code>endStation</code>.</li>\n\t\t<li>The time it takes to travel from <code>startStation</code> to <code>endStation</code> <strong>may be different</strong> from the time it takes to travel from <code>endStation</code> to <code>startStation</code>.</li>\n\t\t<li>There will be at least one customer that has traveled from <code>startStation</code> to <code>endStation</code> before <code>getAverageTime</code> is called.</li>\n\t</ul>\n\t</li>\n</ul>\n\n<p>You may assume all calls to the <code>checkIn</code> and <code>checkOut</code> methods are consistent. If a customer checks in at time <code>t<sub>1</sub></code> then checks out at time <code>t<sub>2</sub></code>, then <code>t<sub>1</sub> < t<sub>2</sub></code>. All events happen in chronological order.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example1:</strong></p>\n\n<pre>\n<strong>Input</strong>\n["UndergroundSystem","checkIn","checkIn","checkIn","checkOut","checkOut","checkOut","getAverageTime","getAverageTime","checkIn","getAverageTime","checkOut","getAverageTime"]\n[[],[45,"Leyton",3],[32,"Paradise",8],[27,"Leyton",10],[45,"Waterloo",15],[27,"Waterloo",20],[32,"Cambridge",22],["Paradise","Cambridge"],["Leyton","Waterloo"],[10,"Leyton",24],["Leyton","Waterloo"],[10,"Waterloo",38],["Leyton","Waterloo"]]\n\n<strong>Output</strong>\n[null,null,null,null,null,null,null,14.00000,11.00000,null,11.00000,null,12.00000]\n\n<strong>Explanation</strong>\nUndergroundSystemundergroundSystem=newUndergroundSystem();\nundergroundSystem.checkIn(45,"Leyton",3);\nundergroundSystem.checkIn(32,"Paradise",8);\nundergroundSystem.checkIn(27,"Leyton",10);\nundergroundSystem.checkOut(45,"Waterloo",15);// Customer 45 "Leyton" -> "Waterloo" in 15-3 = 12\nundergroundSystem.checkOut(27, "Waterloo", 20); // Customer 27 "Leyton" -> "Waterloo" in 20-10 = 10\nundergroundSystem.checkOut(32, "Cambridge", 22); // Customer 32 "Paradise" -> "Cambridge" in 22-8 = 14\nundergroundSystem.getAverageTime("Paradise", "Cambridge"); // return 14.00000. One trip "Paradise" -> "Cambridge", (14) / 1 = 14\nundergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 11.00000. Two trips "Leyton" -> "Waterloo", (10 + 12) / 2 = 11\nundergroundSystem.checkIn(10, "Leyton", 24);\nundergroundSystem.
"code":"public class UndergroundSystem {\n\n public UndergroundSystem() {\n \n }\n \n public void CheckIn(int id, string stationName, int t) {\n \n }\n \n public void CheckOut(int id, string stationName, int t) {\n \n }\n \n public double GetAverageTime(string startStation, string endStation) {\n \n }\n}\n\n/**\n * Your UndergroundSystem object will be instantiated and called as such:\n * UndergroundSystem obj = new UndergroundSystem();\n * obj.CheckIn(id,stationName,t);\n * obj.CheckOut(id,stationName,t);\n * double param_3 = obj.GetAverageTime(startStation,endStation);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"JavaScript",
"langSlug":"javascript",
"code":"\nvar UndergroundSystem = function() {\n \n};\n\n/** \n * @param {number} id \n * @param {string} stationName \n * @param {number} t\n * @return {void}\n */\nUndergroundSystem.prototype.checkIn = function(id, stationName, t) {\n \n};\n\n/** \n * @param {number} id \n * @param {string} stationName \n * @param {number} t\n * @return {void}\n */\nUndergroundSystem.prototype.checkOut = function(id, stationName, t) {\n \n};\n\n/** \n * @param {string} startStation \n * @param {string} endStation\n * @return {number}\n */\nUndergroundSystem.prototype.getAverageTime = function(startStation, endStation) {\n \n};\n\n/** \n * Your UndergroundSystem object will be instantiated and called as such:\n * var obj = new UndergroundSystem()\n * obj.checkIn(id,stationName,t)\n * obj.checkOut(id,stationName,t)\n * var param_3 = obj.getAverageTime(startStation,endStation)\n */",
"code":"-spec underground_system_init_() -> any().\nunderground_system_init_() ->\n .\n\n-spec underground_system_check_in(Id :: integer(), StationName :: unicode:unicode_binary(), T :: integer()) -> any().\nunderground_system_check_in(Id, StationName, T) ->\n .\n\n-spec underground_system_check_out(Id :: integer(), StationName :: unicode:unicode_binary(), T :: integer()) -> any().\nunderground_system_check_out(Id, StationName, T) ->\n .\n\n-spec underground_system_get_average_time(StartStation :: unicode:unicode_binary(), EndStation :: unicode:unicode_binary()) -> float().\nunderground_system_get_average_time(StartStation, EndStation) ->\n .\n\n\n%% Your functions will be called as such:\n%% underground_system_init_(),\n%% underground_system_check_in(Id, StationName, T),\n%% underground_system_check_out(Id, StationName, T),\n%% Param_3 = underground_system_get_average_time(StartStation, EndStation),\n\n%% underground_system_init_ will be called before every test case, in which you can do some necessary initializations.",
"envInfo":"{\"cpp\": [\"C++\", \"<p>Compiled with <code> clang 11 </code> using the latest C++ 20 standard.</p>\\r\\n\\r\\n<p>Your code is compiled with level two optimization (<code>-O2</code>). <a href=\\\"https://github.com/google/sanitizers/wiki/AddressSanitizer\\\" target=\\\"_blank\\\">AddressSanitizer</a> is also enabled to help detect out-of-bounds and use-after-free bugs.</p>\\r\\n\\r\\n<p>Most standard library headers are already included automatically for your convenience.</p>\"], \"java\": [\"Java\", \"<p><code>OpenJDK 17</code>. Java 8 features such as lambda expressions and stream API can be used. </p>\\r\\n\\r\\n<p>Most standard library headers are already included automatically for your convenience.</p>\\r\\n<p>Includes <code>Pair</code> class from https://docs.oracle.com/javase/8/javafx/api/javafx/util/Pair.html.</p>\"], \"python\": [\"Python\", \"<p><code>Python 2.7.12</code>.</p>\\r\\n\\r\\n<p>Most libraries are already imported automatically for your convenience, such as <a href=\\\"https://docs.python.org/2/library/array.html\\\" target=\\\"_blank\\\">array</a>, <a href=\\\"https://docs.python.org/2/library/bisect.html\\\" target=\\\"_blank\\\">bisect</a>, <a href=\\\"https://docs.python.org/2/library/collections.html\\\" target=\\\"_blank\\\">collections</a>. If you need more libraries, you can import it yourself.</p>\\r\\n\\r\\n<p>For Map/TreeMap data structure, you may use <a href=\\\"http://www.grantjenks.com/docs/sortedcontainers/\\\" target=\\\"_blank\\\">sortedcontainers</a> library.</p>\\r\\n\\r\\n<p>Note that Python 2.7 <a href=\\\"https://www.python.org/dev/peps/pep-0373/\\\" target=\\\"_blank\\\">will not be maintained past 2020</a>. For the latest Python, please choose Python3 instead.</p>\"], \"c\": [\"C\", \"<p>Compiled with <code>gcc 8.2</code> using the gnu11 standard.</p>\\r\\n\\r\\n<p>Your code is compiled with level one optimization (<code>-O1</code>). <a href=\\\"https://github.com/google/sanitizers/wiki/AddressSanitizer\\\" target=\\\"_blank\\\">AddressSanitizer</a> is also enabled to help detect out-of-bounds and use-after-free bugs.</p>\\r\\n\\r\\n<p>Most standard library headers are already included automatically for your convenience.</p>\\r\\n\\r\\n<p>For hash table operations, you may use <a href=\\\"https://troydhanson.github.io/uthash/\\\" target=\\\"_blank\\\">uthash</a>. \\\"uthash.h\\\" is included by default. Below are some examples:</p>\\r\\n\\r\\n<p><b>1. Adding an item to a hash.</b>\\r\\n<pre>\\r\\nstruct hash_entry {\\r\\n int id; /* we'll use this field as the key */\\r\\n char name[10];\\r\\n UT_hash_handle hh; /* makes this structure hashable */\\r\\n};\\r\\n\\r\\nstruct hash_entry *users = NULL;\\r\\n\\r\\nvoid add_user(struct hash_entry *s) {\\r\\n HASH_ADD_INT(users, id, s);\\r\\n}\\r\\n</pre>\\r\\n</p>\\r\\n\\r\\n<p><b>2. Looking up an item in a hash:</b>\\r\\n<pre>\\r\\nstruct hash_entry *find_user(int user_id) {\\r\\n struct hash_entry *s;\\r\\n HASH_FIND_INT(users, &user_id, s);\\r\\n return s;\\r\\n}\\r\\n</pre>\\r\\n</p>\\r\\n\\r\\n<p><b>3. Deleting an item in a hash:</b>\\r\\n<pre>\\r\\nvoid delete_user(struct hash_entry *user) {\\r\\n HASH_DEL(users, user); \\r\\n}\\r\\n</pre>\\r\\n</p>\"], \"csharp\": [\"C#\", \"<p><a href=\\\"https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-10\\\" target=\\\"_blank\\\">C# 10 with .NET 6 runtime</a></p>\"], \"javascript\": [\"JavaScript\", \"<p><code>Node.js 16.13.2</code>.</p>\\r\\n\\r\\n<p>Your code is run with <code>--harmony</code> flag, enabling <a href=\\\"http://node.green/\\\" target=\\\"_blank\\\">new ES6 features</a>.</p>\\r\\n\\r\\n<p><a href=\\\"https://lodash.com\\\" target=\\\"_blank\\\">lodash.js</a> library is included by default.</p>\\r\\n\\r\\n<p>For Priority Queue / Queue data structures, you may use 5.3.0 version of <a href=\\\"https://github.com/datastructures-js/priority-queue/tree/fb4fdb984834421279aeb081df7af624d17c2a03\\\" target=\\\"_blank\\\">datastructures-js/priority-queue</a> and 4.2.1 version of <a href=\\\"https://githu
