Solidity solution to Paradigm CTF 2023 Dropper challenge

The Challenge contract invokes the solution contract to airdrop random amounts of ETH, ERC-20 tokens and ERC-721 NFTs to random addresses. The objective is to develop a solution contract that can perform the airdrop using minimal gas.

My submitted score: 1319998

Best score post-CTF, using this trick: 1296955

Summary of optimizations:

Gas	Improvement	Description
1382995		Naive implementation
1380939	2056	Configure compiler optimization for high runs
1346939	34000	Use access-list
1337186	9753	Avoid extra ERC20.transfer
1334819	2367	Avoid for-loops
1322084	12735	Precompute all random values and bake into Solver
1322036	48	payable functions slightly cheaper
1320009	2027	Use fallback function instead of individual functions
*1319998	11	if-condition order makes a tiny difference
1296955	23043	Trick from curta team to use selfdestruct to send ETH cheaply

*My submitted score.

Gas improvements have been committed one by one to make it easy to follow the optimization process.

To run challenge environment:

cd challenge/project/
pkill -9 anvil
anvil --fork-url https://mainnet.infura.io/v3/******************************** --auto-impersonate
forge script --rpc-url http://127.0.0.1:8545 script/Deploy.s.sol:Deploy --broadcast --unlocked --sender $(cast az)

To test solution:

cd ../../solution/
npm install
npm run solve-local

Further gas reductions could be made by writing the solution in a lower-level language like Huff or in EVM bytecode directly.

Enjoy :)