30DaysOfSolidity

Solidity 30 day challenge with codedamn

Goals

Logic building in Solidity
Creation of Smart contracts

DAY 1

Task: Print "Hello Solidity"

Use str as a variable to store value.

DAY 2

Task: Create two seperate functions that returns a state variable and a local variable respectively

Create a state variable and initialize it with 10.
Create a function returnStateVariable( ) which returns the value of the created state variable.
Create a local variable and initialize it with 20.
Create a function returnLocalVariable( ) which returns the value of the created local variable.

DAY 3

Task: Pass an argument to a function

Create a state variable of uint type (need not to be public).
Create a function set() and with one argument. And set the value of the created state variable with the value passed as an argument to the set().
Then create another function get() which returns the value of the state variable.

DAY 4

Task: Write a function that subtracts the difference of two numbers a and b from the sum of a and b

Create a function evaluate(int a , int b).
Subtract the difference of a and b from the sum of a and b.
Return the result of the above task from the evaluate().

DAY 5

Task: Write a function that returns the remainder of a non-negative number when divided by 3

Create a function find(int a). Where a > 0.
Return the remainder when a is divided by 3.

DAY 6

Task: Write a function that returns the average of three numbers

Create a function average(int a,int b,int c). Where a > 0,b > 0,c > 0.
Return the average of a, b and c.

DAY 7

Task: Write a function that returns the sum of digits (n) greater than zero.

Create a function digitSum(int n). Where n > 0.
Return the sum of digit for n.

Example - If n = 345 then digitSum() must return 12 i.e. 3+4+5 = 12 If n = 909 then digitSum() must return 18 i.e. 9+0+9 = 18

DAY 8

Task: Write a function that returns the nth term in a series S, where the next term is the sum of previous three terms.

There is a series, S , where the next term is the sum of pervious three terms. Given the first three terms of the series, a, b ,c and respectively, you have to output the nth term of the series.
```
   S(n) = a for n=1

   S(n) = b for n=2

   S(n) = c for n=3

   S(n) = S(n-1) + S(n-2) + S(n-3) for n>3
```
Create a function nthTerm(uint n, uint a, uint b, uint c) where n is the nth term to find and a, b, c are the three terms of the series.

Example - If n = 5 a = 1 b = 2 c = 3 then nthTerm() must return 11 as S(1) = 1 S(2) = 2 S(3) = 3 S(4) = S(3) + S(2) + S(1) = 1 + 2 + 3 = 6 S(5) = S(4) + S(3) + S(2) = 6 + 3 + 2 = 11

DAY 9

Task: Write a function that returns 1, if the number is a prime number and 0, if it's not.

A prime number is a whole number greater than 1. It has exactly two factors, that is, 1 and the number itself.
Create a function prime(uint n) . This prime() will check whether n is a prime number or not.
If n is a prime number then prime() returns 1 and n is not prime then prime() must return 0.

Example - If n = 103 then prime() must return 1 as 103 is a prime number. If n = 200 then prime() must return 0 as 200 is not a prime number.

DAY 10

Task: Write a function that returns the value of X raised to Y.

If y is a positive integer and x is any real number, then x ^ y corresponds to repeated multiplication x ^ y = x×x×⋯×x y times. We can call this “x raised to the power of y,” “x to the power of y,” or simply “x to the y.” Here, x is the base and y is the exponent or the power.
Create a function power(uint x, uint y) . This power() will calculate x raised to the power of y and return it.

Example - If x = 2 y = 3 then power() must return 8 (2 x 2 x 2 = 8) If x = 7 y = 2then power() must return 49 (7 x 7 = 49)

DAY 11

Task: Write a function that checks if a number is a palindrome or not.

A palindrome number is a number that is same after reverse. For example 545, 151, 34543 etc.
Create a function palindrome(uint n) . This palindrome() will check whether n is a palindrome or not.
If n is a palindrome then palindrome() returns 1 and n is not palindrome then palindrome() must return 0.

Example - If n = 545 then palindrome() must return 1. If n = 123 then palindrome() must return 0.

DAY 12

Task: Write a function that returns the reverse of a number.

Create a function reverseDigit(uint n) . This reverseDigit() will do the reversal of the number n.

Example - If n = 123 then reverseDigit() must return 321. If n = 5342 then reverseDigit() must return 2435.

DAY 13

Task: Write a function that returns the reverse of an array of numbers.

Create a function reverseArray(array, length of array) . This reverseArray() will take two arguments - a dynamic uint type array and length of the array.
The reverseArray() will reverse the array.

For Example - If array = [2,5,9,11,1] then reverseArray() will return [1,11,9,5,2]. If array = [90,20,30,10] then reverseArray() will return [10,30,20,90].

DAY 14

Task: Write a function that converts an array of numbers to even.

Create a function even(array, length of array) . This even() will take two arguments - a dynamic uint type array and length of the array.
The even() will multiply each element of array with 2.

For Example - If array = [2,5,11,1] then even() will return [4,10,22,2,]. If array = [1,3,5,7] then even() will return [2,6,10,14].

DAY 15

Task: Write a function that sorts an array in ascending order.

Create a function sort(array, length of array) . This sort() will take two arguments - a dynamic uint type array and length of the array.
The sort() will sort the array elements in ascending order.

For Example - If array = [2,5,9,11,1] then sort() will return [1,2,5,9,11]. If array = [90,20,30,10] then sort() will return [10,20,30,90].

DAY 16

Task: Write a function that returns the number of distinct elements in an array.

Create a function distinct(array, length of array) . This distinct() will take two arguments - a dynamic uint type array and length of the array.
The distinct() will return the number of distinct elements in an array.

For Example - If array = [4, 2, 3, 4] then distinct() will return 3. If array = [1, 1, 1] then distinct() will return 1.

DAY 17

Task: Write a function that checks if an element is in an array.

Create a function search(array, length of array,element to search) . This search() will take three arguments - a dynamic uint type array ,length of the array, element that we need to search.
The search() will search an element in an array.
If element is found then it will return 1 otherwise 0.

For Example - If array = [4, 2, 3, 4] search element = 2 then search() will return 1. If array = [1, 2, 3] search element = 4 then search() will return 0.

DAY 18

Task: Write a function that returns the sum of an array.

Create a function sumArray(array, length of array) . This sumArray() will take two arguments - a dynamic int type array and length of the array.
The sumArray() will add all elements of an array.

For Example - If array = [4, 2, 3, 4] then sumArray() will return 13 i.e. 4 + 2 + 3 + 4 = 13 If array = [1, 2, 3] then sumArray() will return 6 i.e. 1 + 2 + 3 = 6.

DAY 19

Task: Write a function that returns the sum of the series `1 + x + x^2+ x^3+ .. + x^n`

Create a function expression(x, n).
The expression() will find the sum of the above expression.

For Example - If x = 2 n = 3 then expression() will return 15. If x = 5 n = 1 then expression() will return 6.

DAY 20

Task: Write a function that returns the second largest element in an array.

Create a function secondMax(array, length of array) . This secondMax() will take two arguments - a dynamic int type array and length of the array.
The secondMax() will find the second largest element in an array.

For Example - If array = [40, 12, 31, 6] then secondMax() will return 31. If array = [9, 122, 37, 54] then secondMax() will return 54.

DAY 21

Task: Write a function that returns the highest common factor (HCF) of two numbers.

Create a function hcf(num1,num2) . This hcf() will take two arguments uint type number1 and number2.
The hcf() will find the of number1 and number2.

For Example - If num1 = 60 num2 = 75 then hcf() will return 15. If num1 = 31 and num2 = 23 then hcf() will return 1.

DAY 22

Task: Define a structure (struct). Write setter and getter function use cases for it.

Create a structure -> struct Book { string title; string author; uint256 book_id; }
Create two functions

a) setBook(title(string),author(string),id(uint)) - To set the book title, author and id given in the structure.

b) getBook() - To get the book title, author and id.

DAY 23

Task: Define an array of structure (struct). Write setter and getter function use cases for it.

Create "Book type" dynamic array. This "Book type" array will contain different types of Book.
Create a counter( initialized by 1) which increases every time when a Book is added to the "Book type" array. This counter will act as a id for the Books added in the "Book type" array. Every Book in the "Book type" array will have a unique id.
Create two functions

a) setBook(title(string), author(string), id(uint)) - To set the book title, author and id given in the "Book type" array.

b) getBook(id(uint)) - To get the book title, author and id of the Book whose id is passed as an argument.

DAY 24

Task: Define an array within a structure (struct). Write setter and getter function use cases for it.

Create a structure -> struct Student { string name; uint256[3] marks; }
Create two functions

a) set(name of student, marks in maths, marks in science, marks in english) - To set the name and marks of a student in marks array.

b) get() - To get the name, marks in maths, marks in science and marks in english of the student.

DAY 25

Task: Define an enum. Write setter and getter function use cases for it.

Create an -> enum House { SMALL, MEDIUM, LARGE }
Create a variable of enum type.
Create a function setLarge(). This will set the value of the enum type variable (created at step 2) with LARGE.
Create a function getChoice() which will return the value of the enum type variable (created at step 2) .

DAY 26

Task: Write a function that returns the address of the owner of a contract.

Create a constructor() to hold the address of the owner. [Hint: use msg.sender].
Create a function returnOwner() which returns the address of the owner.
This returnOwner() can only be called by the owner (that we set using constructor()). If some other address tries to call this returnOwner(), it should revert with this statement "You are not the owner".

DAY 27

Task: Define a mapping, write functions to update and retrieve values from a mapping.

Create a mapping(address => uint256).
Create a function updateBalance(balance to update) . This updateBalance() will take one argument - a uint type variable. This function will update the balance of the address who has called this updateBalance().
Create a function checkBalance(address of a user) . This checkBalance(address user) will take one argument - a address type variable. This function will return the balance of the user who has called this function. With this function user can only check his/her own balance only. If the user tries to check some other address balance the checkBalance() should revert with "You are not the owner of the account".

DAY 28

Task: Write a function to transfer amount.

Create a constructor() to set the owner of contract . [Hint: use msg.sender]
Create a payable function send(address type array for storing addresses, uint type array to store the amount). This send() will do the following -
The send() can only be called by owner of the contract.
Check whehter the length of the address array is equal to length of the amount array. If not revert with "to must be same length as amount".
If the length of both array are equal. Then it will transfer the amount from the amount array to the address array in such a way address at ith index of address array receives the amount at ith index of amount array.
For Example - If address array =[0x412, 0x2ab, 0x3de] and amount array = [10,5,90] then send() will transfer amount 10 to address 0x412 , amount 5 to address 0x2ab, amount 90 to address 03de.

DAY 29

Task: Write a function which returns the addresses of team players.

Create an array which stores addresses of the team players.
Create an array(address type) which stores only 16 elements.
getTeamPlayers() - To return the entire array elements.
selectJerseyNumber() - It will take only one argument of uint type and returns the players address from the array created above.
```
a) The argument passed into the function must be greater than equal to zero and less than equal to 15. [Hint - Use require]
```

DAY 30

Task: Write a function that concatenates two strings and returns the value of the concatenated strings.

concatenate() - This function will take two arguments i.e string 1 and string 2. It will concatenate string 1 and string 2 and will return the concatenated string.

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