Project Euler #5 : Smallest multiple

2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.

What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?

Solution

using System; using System.Collections.Generic; using System.IO; class Solution {     static void Main(String[] args) {          int testCases = Convert.ToInt32(Console.ReadLine());             int[] numbers = new int[testCases];             for (int i = 0; i < testCases; i++)             {                 numbers[i] = Convert.ToInt32(Console.ReadLine());             }             foreach (int number in numbers)             {                 long product = 1;                 for (int i = 2; i <= number; i++)                 {                     if(IsPrime(i))                     {                         int temp = i;                         for(int j=2;j<=number;j++)                         {                             if(Math.Pow(Convert.ToDouble(i),Convert.ToDouble(j))>number)                             {                                 break;                             }                             else                             {                                 temp = Convert.ToInt32(Math.Pow(Convert.ToDouble(i), Convert.ToDouble(j)));                             }                         }                         product = product * temp;                     }                 }                 Console.WriteLine(product);             }     }     public static bool IsPrime(int number)         {             if (number == 2 || number == 3)                 return true;             else             {                 bool flag = true;                 for (int i = 2; i <= Math.Sqrt(number); i++)                 {                     if (number % i == 0)                     {                         flag = false;                         break;                     }                 }                 return flag;             }         } }

Project Euler #4 : Largest palindrome product

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.

Find the largest palindrome made from the product of two 3-digit numbers

Solution

using System; using System.Collections.Generic; using System.IO; class Solution {     static void Main(String[] args) {          int testCases = Convert.ToInt32(Console.ReadLine());             List<int> numbers = new List<int>();             for (int k = 0; k < testCases; k++)             {                 numbers.Add(Convert.ToInt32(Console.ReadLine()));             }             foreach (int number in numbers)             {                 Console.WriteLine(FindLargestNumber(number));             }     }     public static int FindLargestNumber(int number)         {             for (int x = 9; x >= 0; --x)             {                 int a = x * 100001;                 for (int y = 9; y >= 0; --y)                 {                     int b = a + y * 10010;                     for (int z = 9; z >= 0; --z)                     {                         int n = b + z * 1100;                         if (n < number)                         {                             for (int i = 990; i > 99; i -= 11)                             {                                 if (n % i == 0)                                 {                                     int t = n / i;                                     if (t < 1000) return n;                                 }                             }                         }                     }                 }             }             return 0;         } }

Project Euler #3: Largest prime factor

Today I will show how to solve Project Euler Problem 3

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of a given number N?

Input Format
First line contains T, the number of test cases. This is followed by T lines each containing an integer N.

Output Format
For each test case, display the largest prime factor of N.

Constraints
1≤T≤10
10≤N≤1012

Sample Input

2

10

17

Sample Output

5

17

Solution

int T = int.Parse(Console.ReadLine()); long[] numbers = new long[T]; for (int i = 0; i < T; i++) {     numbers[i] = Int64.Parse(Console.ReadLine()); } for (int i = 0; i < T; i++) {     long num = numbers[i];     int a = 3;     while (num % 2 == 0)       num = num / 2;     if (num == 1)       num = 2;     while (a <= Math.Sqrt(num))     {       if (num % a == 0)       {         num = num / a;         continue;                         //a --;       }         a = a + 2;     }       Console.WriteLine(num); }

Project Euler #2: Even Fibonacci numbers

Hi folks, today I will show you how to solve Project Euler Problem 2.

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1,2,3,5,8,13,21,34,55,89,⋯

By considering the terms in the Fibonacci sequence whose values do not exceed N, find the sum of the even-valued terms.

Solution

int i = Convert.ToInt32(Console.ReadLine()); List<decimal> list = new List<decimal>(); for (int j = 0; j < i; j++) {    list.Add(Convert.ToInt64(Console.ReadLine())); } foreach (decimal k in list) {    long b = 1;    long c = 2, d;    long sum = 0;    while (c < k)    {       sum += c;       d = b + (c << 0x01);       c = d + b + c;       b = d;    }    Console.WriteLine(sum); }

Project Euler #1: Multiples of 3 and 5

Hi guys, today I will show you how to solve Project Euler Problem 1, the question is

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000000000.

I tried to solve this question using for loop. It was working fine but it was taking so many times to get the result. Then I implemented some mathematical logic to solve this issue.

static void Main(String[] args) {             int i = Convert.ToInt32(Console.ReadLine());             List<long> list = new List<long>();             for (int j = 0; j < i; j++)             {                 list.Add(Convert.ToInt64(Console.ReadLine()));             }             foreach(long k in list)             {                 long sum=0;                 long i3 = (((k - 1) / 3) * (((k - 1) / 3) + 1)) / 2;                 sum += i3 * 3;                 long i5 = (((k - 1) / 5) * (((k - 1) / 5) + 1)) / 2;                 sum += i5 * 5;                 long i15 = (((k - 1) / 15) * (((k - 1) / 15) + 1)) / 2;                 sum -= i15 * 15;                 Console.WriteLine(sum);             }     }

How to clear the values entered in the textbox by pressing F5 or Refreshing the page

Hi guys, today I will show you how to clear the textbox value when you press F5, This will also prevent you from submission of data when you press F5.

First create a design page like this

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server">     <title></title> </head> <body>     <form id="form1" runat="server">     <div>        First Name :  <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox><br />        Last Name : <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox><br />        <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />     </div>     </form> </body> </html>

Now write the following code in aspx.cs page

protected void Page_Load(object sender, EventArgs e)     {         if(!IsPostBack)         {             Session["Submitted"] = false;         }         if(Convert.ToBoolean(Session["submitted"].ToString())==true)         {             TextBox1.Text = string.Empty;             TextBox2.Text = string.Empty;         }     }     protected void Button1_Click(object sender, EventArgs e)     {         Session["Submitted"] = true;     }

Linq to XML Example 1

Hi guys, today I will show you one demo on LINQ to XML, this is very very helpful for the beginners who are trying to learn LINQ. Here I have prepared one demo like I have a xml file with list of employees, when a user give the employee ID it should populate the employee Name.

First Create a XML File

<?xml version="1.0" encoding="utf-8" ?> <Employees>   <Employee>     <ID>001</ID>     <Name>Rohit</Name>   </Employee>   <Employee>     <ID>002</ID>     <Name>Sam</Name>   </Employee>   <Employee>     <ID>003</ID>     <Name>Jonshon</Name>   </Employee>   <Employee>     <ID>004</ID>     <Name>Rocky</Name>   </Employee> </Employees>

Then design the page like this

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server">     <title></title> </head> <body>     <form id="form1" runat="server">     <div>             Enter ID :         <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> &nbsp;         <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Submit" />         <br />         <br />         <asp:Label ID="Label1" runat="server"></asp:Label>         </div>     </form> </body> </html>

Now write the following code in the aspx.cs file

using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using System.Xml; using System.Xml.Linq; public partial class _Default : System.Web.UI.Page {     protected void Page_Load(object sender, EventArgs e)     {     }     protected void Button1_Click(object sender, EventArgs e)     {         XElement obj = XElement.Load(Server.MapPath("~/XMLFile.xml"));               string employeeName= obj.Descendants("Employee")                             .Where(x => (string)x.Element("ID") == TextBox1.Text)                             .Select(x=>(string)x.Element("Name")).SingleOrDefault();        if (!string.IsNullOrEmpty(employeeName))        {            Label1.Text = employeeName;        }        else        {            Label1.Text = "No Employee";        }     } }

Demo