update

Author: hijiangtao

README.md

@@ -2,19 +2,22 @@
 
 This is the solution collection of my LeetCode problems, most of them are programmed in JavaScript.
 
-Progress: 14/
+Progress: 18/
 
 | ID | Title | Solution | Difficulty |
 |---| ----- | -------- | ---------- |
 |1|[Two Sum](https://leetcode.com/problems/two-sum/) | [JavaScript](./src/two-sum/res.js)|Easy|
 |2|[Add Two Numbers](https://leetcode.com/problems/add-two-numbers/) | [JavaScript](./src/add-two-numbers/res.js)|Medium|
+|7|[Reverse Integer](https://leetcode.com/problems/reverse-integer/) | [JavaScript](./src/reverse-integer/res.js)|Easy|
+|13|[Roman to Integer](https://leetcode.com/problems/roman-to-integer/) | [JavaScript](./src/roman-to-integer/res.js)|Easy|
 |66|[Plus One](https://leetcode.com/problems/plus-one/) | [JavaScript](./src/plus-one/res.js)|Easy|
 |69|[Sqrt(x)](https://leetcode.com/problems/sqrtx/) | [JavaScript](./src/sqrtx/res.js)|Easy|
 |175|[Combine Two Tables](https://leetcode.com/problems/combine-two-tables/)| [SQL](./src/combine-two-tables/res.txt)|Easy|
 |176|[Second Highest Salary](https://leetcode.com/problems/second-highest-salary/)| [SQL](./src/second-highest-salary/res.txt)|Easy|
 |177|[Nth Highest Salary](https://leetcode.com/problems/nth-highest-salary/)| [SQL](./src/nth-highest-salary/res.txt)|Medium|
 |181|[Employees Earning More Than Their Managers](https://leetcode.com/problems/employees-earning-more-than-their-managers/) | [SQL](./src/employees-earning-more-than-their-managers/res.txt)|Easy|
 |182|[Duplicate Emails](https://leetcode.com/problems/duplicate-emails/) | [SQL](./src/duplicate-emails/res.txt)|Easy|
+|183|[Customers Who Never Order](https://leetcode.com/problems/customers-who-never-order/) | [SQL](./src/customers-who-never-order/res.txt)|Easy|
 |184|[Department Highest Salary](https://leetcode.com/problems/department-highest-salary/) | [SQL](./src/department-highest-salary/res.txt)|Medium|
 |196|[Delete Duplicate Emails](https://leetcode.com/problems/delete-duplicate-emails/) | [SQL](./src/delete-duplicate-emails/res.txt)|Easy|
 |197|[Rising Temperature](https://leetcode.com/problems/rising-temperature/) | [SQL](./src/rising-temperature/res.txt)|Easy|

src/customers-who-never-order/res.txt

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+-- Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything.
+
+-- Table: Customers.
+
+-- +----+-------+
+-- | Id | Name  |
+-- +----+-------+
+-- | 1  | Joe   |
+-- | 2  | Henry |
+-- | 3  | Sam   |
+-- | 4  | Max   |
+-- +----+-------+
+-- Table: Orders.
+
+-- +----+------------+
+-- | Id | CustomerId |
+-- +----+------------+
+-- | 1  | 3          |
+-- | 2  | 1          |
+-- +----+------------+
+-- Using the above tables as example, return the following:
+
+-- +-----------+
+-- | Customers |
+-- +-----------+
+-- | Henry     |
+-- | Max       |
+-- +-----------+
+
+# Write your MySQL query statement below
+SELECT Name AS 'Customers' FROM Customers WHERE Id NOT IN (SELECT DISTINCT(CustomerId) FROM Orders);

src/reverse-integer/res.js

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+/**
+ * Reverse digits of an integer.
+ * 
+ * Example1: x = 123, return 321
+ * Example2: x = -123, return -321
+ * 
+ * Note:
+ * The input is assumed to be a 32-bit signed integer. Your function should return 0 when the reversed integer overflows.
+ * 
+ * res.js
+ * @authors Joe Jiang (hijiangtao@gmail.com)
+ * @date    2017-02-21 21:25:59
+ * @version $Id$
+ */
+
+/**
+ * @param {number} x
+ * @return {number}
+ */
+var reverse = function(x) {
+    let res = 0,
+    	abs = Math.abs(x),
+    	negative = abs === x? false:true;
+
+    while (abs>0) {
+    	let currentVal = abs % 10;
+    	res = res*10 + currentVal;
+    	abs = Number.parseInt(abs/10);
+    }
+
+    if (res > Math.pow(2, 31)) {
+    	return 0;
+    } else if (negative) {
+    	return -res;
+    }
+
+    return res;
+};
+
+// Another solution wrote in Java
+// 
+// public int reverse(int x)
+// {
+//     int result = 0;
+
+//     while (x != 0)
+//     {
+//         int tail = x % 10;
+//         int newResult = result * 10 + tail;
+//         if ((newResult - tail) / 10 != result)
+//         { return 0; }
+//         result = newResult;
+//         x = x / 10;
+//     }
+
+//     return result;
+// }

src/roman-to-integer/res.js

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+/**
+ * From the following table, find the highest roman numeral (n) with the highest decimal value (v)
+ * that is taken from the left part of the roman numeral r
+ *
+ * From http://www.rapidtables.com/convert/number/how-roman-numerals-to-number.htm
+ * 
+ * I	1
+ * IV	4
+ * V	5
+ * IX	9
+ * X	10
+ * XL	40
+ * L	50
+ * XC	90
+ * C	100
+ * CD	400
+ * D	500
+ * CM	900
+ * M	1000
+ * res.js
+ * @authors Your Name (you@example.org)
+ * @date    2017-02-21 22:06:00
+ * @version $Id$
+ */
+
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var romanToInt = function(s) {
+	let res = 0;
+    while (s) {
+        if (s.indexOf('M') === 0) {
+        	res += 1000;
+        	s = s.substring(1);
+        } else if (s.indexOf('CM') === 0) {
+        	res += 900;
+        	s = s.substring(2);
+        } else if (s.indexOf('D') === 0) {
+        	res += 500;
+        	s = s.substring(1);
+        } else if (s.indexOf('CD') === 0) {
+        	res += 400;
+        	s = s.substring(2);
+        } else if (s.indexOf('C') === 0) {
+        	res += 100;
+        	s = s.substring(1);
+        } else if (s.indexOf('XC') === 0) {
+        	res += 90;
+        	s = s.substring(2);
+        } else if (s.indexOf('L') === 0) {
+        	res += 50;
+        	s = s.substring(1);
+        } else if (s.indexOf('XL') === 0) {
+        	res += 40;
+        	s = s.substring(2);
+        } else if (s.indexOf('X') === 0) {
+        	res += 10;
+        	s = s.substring(1);
+        } else if (s.indexOf('IX') === 0) {
+        	res += 9;
+        	s = s.substring(2);
+        } else if (s.indexOf('V') === 0) {
+        	res += 5;
+        	s = s.substring(1);
+        } else if (s.indexOf('IV') === 0) {
+        	res += 4;
+        	s = s.substring(2);
+        } else if (s.indexOf('I') === 0) {
+        	res += 1;
+        	s = s.substring(1);
+        }
+    }
+
+    return res;
+};