projecteuler.net is a very helpful website for new programmers to increase their problem solving skills using programming. So far, I have been able to solve 23 problems. Following is the description of the problem that I have solved in the code that I have uploaded in this folder

Problem 19
Counting Sundays

You are given the following information, but you may prefer to do some research for yourself.

1 Jan 1900 was a Monday. Thirty days has September, April, June and November. All the rest have thirty-one, Saving February alone, Which has twenty-eight, rain or shine. And on leap years, twenty-nine. A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400. How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?

My solution is not really elegent as I would hoped to find but it works. This problem was difficult to think about.

Problem 21
Amicable Numbers

Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide evenly into n). If d(a) = b and d(b) = a, where a ≠ b, then a and b are an amicable pair and each of a and b are called amicable numbers.

For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110; therefore d(220) = 284. The proper divisors of 284 are 1, 2, 4, 71 and 142; so d(284) = 220.

Evaluate the sum of all the amicable numbers under 10000.

Problem 22
Maximum path sum

It is appropriate that I give a URL to this problem,
https://projecteuler.net/problem=18
https://projecteuler.net/problem=67

Problem 18 and 67 are the same problems with different magnitutude of difficulty. I apologize if I am causing confusion in the problem number, I was programming I though it was 22 but it is 18, 67 on the website.

Problem 24
Lexicographic Permutations

A permutation is an ordered arrangement of objects. For example, 3124 is one possible permutation of the digits 1, 2, 3 and 4. If all of the permutations are listed numerically or alphabetically, we call it lexicographic order. The lexicographic permutations of 0, 1 and 2 are:

012 021 102 120 201 210

What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?

This was another difficult problem that I tried to solve but couldn't find good solution. The pattern is easy to spot but difficult to write in terms of math/code. There is an algoirthm avaiable to solve this problem and I just tried to code that algorithm in C++.