Added tasks 262-264.

src/main/java/g0201_0300/s0262_trips_and_users/readme.md

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+262\. Trips and Users
+
+Hard
+
+SQL Schema
+
+Table: `Trips`
+
+ +-------------+----------+
+ | Column Name | Type |
+ +-------------+----------+
+ | id | int |
+ | client_id | int |
+ | driver_id | int |
+ | city_id | int |
+ | status | enum |
+ | request_at | date |
+ +-------------+----------+
+ id is the primary key for this table.
+ The table holds all taxi trips. Each trip has a unique id, while client_id and driver_id are foreign keys to the users_id at the Users table.
+ Status is an ENUM type of ('completed', 'cancelled_by_driver', 'cancelled_by_client'). 
+
+Table: `Users`
+
+ +-------------+----------+
+ | Column Name | Type |
+ +-------------+----------+
+ | users_id | int |
+ | banned | enum |
+ | role | enum |
+ +-------------+----------+
+ users_id is the primary key for this table.
+ The table holds all users. Each user has a unique users_id, and role is an ENUM type of ('client', 'driver', 'partner').
+ banned is an ENUM type of ('Yes', 'No'). 
+
+The **cancellation rate** is computed by dividing the number of canceled (by client or driver) requests with unbanned users by the total number of requests with unbanned users on that day.
+
+Write a SQL query to find the **cancellation rate** of requests with unbanned users (**both client and driver must not be banned**) each day between `"2013-10-01"` and `"2013-10-03"`. Round `Cancellation Rate` to **two decimal** points.
+
+Return the result table in **any order**.
+
+The query result format is in the following example.
+
+**Example 1:**
+
+**Input:**
+
+ Trips table:
+ +----+-----------+-----------+---------+---------------------+------------+
+ | id | client_id | driver_id | city_id | status | request_at |
+ +----+-----------+-----------+---------+---------------------+------------+
+ | 1 | 1 | 10 | 1 | completed | 2013-10-01 |
+ | 2 | 2 | 11 | 1 | cancelled_by_driver | 2013-10-01 |
+ | 3 | 3 | 12 | 6 | completed | 2013-10-01 |
+ | 4 | 4 | 13 | 6 | cancelled_by_client | 2013-10-01 |
+ | 5 | 1 | 10 | 1 | completed | 2013-10-02 |
+ | 6 | 2 | 11 | 6 | completed | 2013-10-02 |
+ | 7 | 3 | 12 | 6 | completed | 2013-10-02 |
+ | 8 | 2 | 12 | 12 | completed | 2013-10-03 |
+ | 9 | 3 | 10 | 12 | completed | 2013-10-03 |
+ | 10 | 4 | 13 | 12 | cancelled_by_driver | 2013-10-03 |
+ +----+-----------+-----------+---------+---------------------+------------+
+
+ Users table:
+
+ +----------+--------+--------+
+ | users_id | banned | role |
+ +----------+--------+--------+
+ | 1 | No | client |
+ | 2 | Yes | client |
+ | 3 | No | client |
+ | 4 | No | client |
+ | 10 | No | driver |
+ | 11 | No | driver |
+ | 12 | No | driver |
+ | 13 | No | driver |
+ +----------+--------+--------+
+
+**Output:**
+
+ +------------+-------------------+
+ | Day | Cancellation Rate |
+ +------------+-------------------+
+ | 2013-10-01 | 0.33 |
+ | 2013-10-02 | 0.00 |
+ | 2013-10-03 | 0.50 |
+ +------------+-------------------+
+
+**Explanation:**
+
+ On 2013-10-01:
+ - There were 4 requests in total, 2 of which were canceled.
+ - However, the request with Id=2 was made by a banned client (User_Id=2), so it is ignored in the calculation.
+ - Hence there are 3 unbanned requests in total, 1 of which was canceled.
+ - The Cancellation Rate is (1 / 3) = 0.33
+ On 2013-10-02:
+ - There were 3 requests in total, 0 of which were canceled.
+ - The request with Id=6 was made by a banned client, so it is ignored.
+ - Hence there are 2 unbanned requests in total, 0 of which were canceled.
+ - The Cancellation Rate is (0 / 2) = 0.00
+ On 2013-10-03:
+ - There were 3 requests in total, 1 of which was canceled.
+ - The request with Id=8 was made by a banned client, so it is ignored.
+ - Hence there are 2 unbanned request in total, 1 of which were canceled.
+ - The Cancellation Rate is (1 / 2) = 0.50 

src/main/java/g0201_0300/s0262_trips_and_users/script.sql

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+# Write your MySQL query statement below
+SELECT T.Request_at AS Day, ROUND(SUM(if(T.Status <> 'completed', 1,0))/COUNT(*),2) AS `Cancellation Rate` FROM Trips AS T LEFT JOIN (SELECT * FROM Users WHERE Role = 'client') AS C ON T.Client_Id = C.Users_Id LEFT JOIN (SELECT * FROM Users WHERE Role = 'driver') AS D ON T.Driver_Id = D.Users_Id WHERE C.Banned <> 'YES' AND D.Banned <> 'YES' AND T.Request_at BETWEEN '2013-10-01' AND '2013-10-03' GROUP BY T.Request_at ORDER BY Day;

src/main/java/g0201_0300/s0263_ugly_number/Solution.java

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+package g0201_0300.s0263_ugly_number;
+
+public class Solution {
+ public boolean isUgly(int n) {
+ if (n == 1) {
+ return true;
+ } else if (n <= 0) {
+ return false;
+ }
+ int[] factors = new int[] {2, 3, 5};
+ for (int factor : factors) {
+ while (n > 1 && n % factor == 0) {
+ n /= factor;
+ }
+ }
+ return n == 1;
+ }
+}

src/main/java/g0201_0300/s0263_ugly_number/readme.md

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+263\. Ugly Number
+
+Easy
+
+An **ugly number** is a positive integer whose prime factors are limited to `2`, `3`, and `5`.
+
+Given an integer `n`, return `true` _if_ `n` _is an **ugly number**_.
+
+**Example 1:**
+
+**Input:** n = 6
+
+**Output:** true
+
+**Explanation:** 6 = 2 × 3
+
+**Example 2:**
+
+**Input:** n = 8
+
+**Output:** true
+
+**Explanation:** 8 = 2 × 2 × 2 
+
+**Example 3:**
+
+**Input:** n = 14
+
+**Output:** false
+
+**Explanation:** 14 is not ugly since it includes the prime factor 7. 
+
+**Example 4:**
+
+**Input:** n = 1
+
+**Output:** true
+
+**Explanation:** 1 has no prime factors, therefore all of its prime factors are limited to 2, 3, and 5. 
+
+**Constraints:**
+
+* <code>-2<sup>31</sup> <= n <= 2<sup>31</sup> - 1</code>

src/main/java/g0201_0300/s0264_ugly_number_ii/Solution.java

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+package g0201_0300.s0264_ugly_number_ii;
+
+public class Solution {
+ public int nthUglyNumber(int n) {
+ int[] ugly = new int[n];
+ int i2 = 0;
+ int i3 = 0;
+ int i5 = 0;
+ int ugly2 = 2;
+ int ugly3 = 3;
+ int ugly5 = 5;
+ int nextugly = 1;
+ ugly[0] = 1;
+ for (int i = 1; i < n; i++) {
+ nextugly = Math.min(Math.min(ugly2, ugly3), ugly5);
+ ugly[i] = nextugly;
+ if (nextugly == ugly2) {
+ i2++;
+ ugly2 = ugly[i2] * 2;
+ }
+ if (nextugly == ugly3) {
+ i3++;
+ ugly3 = ugly[i3] * 3;
+ }
+ if (nextugly == ugly5) {
+ i5++;
+ ugly5 = ugly[i5] * 5;
+ }
+ }
+ return ugly[n - 1];
+ }
+}

src/main/java/g0201_0300/s0264_ugly_number_ii/readme.md

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+264\. Ugly Number II
+
+Medium
+
+An **ugly number** is a positive integer whose prime factors are limited to `2`, `3`, and `5`.
+
+Given an integer `n`, return _the_ <code>n<sup>th</sup></code> _**ugly number**_.
+
+**Example 1:**
+
+**Input:** n = 10
+
+**Output:** 12
+
+**Explanation:** \[1, 2, 3, 4, 5, 6, 8, 9, 10, 12\] is the sequence of the first 10 ugly numbers. 
+
+**Example 2:**
+
+**Input:** n = 1
+
+**Output:** 1
+
+**Explanation:** 1 has no prime factors, therefore all of its prime factors are limited to 2, 3, and 5. 
+
+**Constraints:**
+
+* `1 <= n <= 1690`

src/test/java/g0201_0300/s0263_ugly_number/SolutionTest.java

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+package g0201_0300.s0263_ugly_number;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.Test;
+
+public class SolutionTest {
+ @Test
+ public void isUgly() {
+ assertThat(new Solution().isUgly(6), equalTo(true));
+ }
+
+ @Test
+ public void isUgly2() {
+ assertThat(new Solution().isUgly(8), equalTo(true));
+ }
+
+ @Test
+ public void isUgly3() {
+ assertThat(new Solution().isUgly(14), equalTo(false));
+ }
+
+ @Test
+ public void isUgly4() {
+ assertThat(new Solution().isUgly(1), equalTo(true));
+ }
+}

src/test/java/g0201_0300/s0264_ugly_number_ii/SolutionTest.java

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+package g0201_0300.s0264_ugly_number_ii;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.Test;
+
+public class SolutionTest {
+ @Test
+ public void nthUglyNumber() {
+ assertThat(new Solution().nthUglyNumber(10), equalTo(12));
+ }
+
+ @Test
+ public void nthUglyNumber2() {
+ assertThat(new Solution().nthUglyNumber(1), equalTo(1));
+ }
+}