Solidity Programming Problems, Sample Smart Contracts, and Vulnerable Codes

This README provides a comprehensive collection of Solidity programming problems, sample decentralized applications (DApps), and examples of vulnerable code. Each section includes solutions to help you understand and solve these issues effectively. The questions and examples are sourced from platforms like Alchemy University, Calyptus, Code Wars, DappWorld, Ethernaut, and Ethereum Stack Exchange.

Table of Contents

1. Programming Problems
2. Sample Contracts
3. Vulnerable Code Examples
4. Solidity Codewars Solutions

Programming Problems

Problem ID	Description	Solution
PP-01	DataTypes of Solidity.	Solution
PP-02	Constructors of Solidity.	Solution
PP-03	Variables of Solidity.	Solution
PP-04	Functions of Solidity.	Solution
PP-05	Visibility of Solidity.	Solution
PP-06	Pure View Functions of Solidity.	Solution
PP-07	Function Modifiers of Solidity.	Solution
PP-08	Arrays of Solidity.	Solution
PP-09	Events of Solidity.	Solution
PP-10	Error Handling of Solidity.	Solution
PP-11	Value Types of Solidity.	Solution
PP-12	Fallback Functions of Solidity.	Solution
PP-13	For Loop of Solidity.	Solution
PP-14	Mapping of Solidity.	Solution
PP-15	Enum of Solidity.	Solution
PP-16	Struct of Solidity.	Solution
PP-17	Payable Modifier of Solidity.	Solution
PP-18	Imports of Solidity.	Solution
PP-19	Contract CleanUp of Solidity.	Solution
PP-20	Memory & Storage of Solidity.	Solution
PP-21	Inheritance of Solidity.	Solution
PP-22	If Statement of Solidity.	Solution
PP-23	Libraries of Solidity.	Solution
PP-24	Interface of Solidity.	Solution

Sample Contracts

DApp ID	Description	Solution
SD-01	Address book Solidity smart contract.	Solution
SD-02	An ERC721 Calyptus NFT contract.	Solution
SD-03	A dynamic pricing model for a decentralized storage contract.	Solution
SD-04	A transfer ownership of an in-game asset contract.	Solution
SD-05	A ERC721 safemint Token contract.	Solution
SD-06	A trustless escrow system contract contract.	Solution
SD-07	An ERC1155 Event ticket contract.	Solution
SD-08	A hotel room contract.	Solution
SD-09	A lottery, where users can buy tickets contract.	Solution
SD-10	A simple contract.	Solution
SD-11	An ERC20 token smart contract.	Solution
SD-12	A NFT ERC721 with alchemy contract.	Solution
SD-13	An users make payments to the owner smart contract.	Solution
SD-14	An users can rent storage space in exchange for tokens contract.	Solution
SD-15	A Shared Wallet contract.	Solution
SD-16	A function to implement a staking system, where users can earn rewards contract.	Solution
SD-17	OTT Subscription based on tiers and basic to annual pack contract.	Solution
SD-18	A time lock contract.	Solution
SD-19	A function to implement a voting system contract.	Solution
SD-20	A withdraw funds contract.	Solution
SD-21	A Delegate call to upgrade a solidity smart contract.	Solution

Vulnerable Code Examples

Vulnerability ID	Description	Solution
VC-01	Re-entrancy vulnerability.	Solution
VC-02	tx.origin phishing vulnerability.	Solution
VC-03	Arithmetic overflow/underflow vulnerability.	Solution
VC-04	FrontRunning vulnerability.	Solution
VC-05	DoS vulnerability.	Solution
VC-06	Oracle Manipulation vulnerability.	Solution
VC-07	TimeStamp Manipulation vulnerability.	Solution

Solidity Codewars Solutions

• This repository contains Solidity solutions for various Codewars challenges focused on fundamentals, arrays, algorithms, and beginner-friendly smart contract implementations - README

Problem ID	Description	Solution
FND-01	Is n Divisible by x and y?	Solution
FND-02	Grasshopper - Summation	Solution
FND-03	String Repeat	Solution
FND-04	Century From Year	Solution
FND-05	Multiply	Solution
FND-06	Sum of Odd Numbers	Solution
FND-07	Count by X	Solution
FND-08	Roman Numerals Encoder	Solution
FND-09	Expressions Matter	Solution
FND-10	Sum of Angles	Solution
FND-11	Maximum Multiple	Solution
FND-12	Grasshopper - Check for Factor	Solution
FND-13	Beginner Series #2 Clock	Solution
FND-14	Third Angle of a Triangle	Solution
SC-01	HelloWorld Smart Contract	Solution
SC-02	Rock, Paper, Scissors Smart Contract	Solution
SC-03	Grasshopper - Terminal Game Move Function	Solution
SC-04	Tic-Tac-Toe Checker	Solution

Resources

• Solidity Documentation
• OpenZeppelin Contracts
• Smart Contract Security Best Practices
• Alchemy Documentation
• Cyfrin