# Swap V3 to V4 Exercises In this exercise, you'll learn how to use the [`UniversalRouter`](https://github.com/Uniswap/universal-router/blob/main/contracts/UniversalRouter.sol) contract to execute a multi hop swap from V3 to V4. The starter code for this exercise is provided in [`foundry/src/exercises/SwapV3ToV4.sol`](https://github.com/Cyfrin/defi-uniswap-v4/blob/main/foundry/src/exercises/SwapV3ToV4.sol) Solution is in [`foundry/src/solutions/SwapV3ToV4.sol`](https://github.com/Cyfrin/defi-uniswap-v4/blob/main/foundry/src/solutions/SwapV3ToV4.sol) ## Task 1 - Swap ```solidity function swap(V3Params calldata v3, V4Params calldata v4) external {} ``` Call `UniversalRouter` to swap token `A` to `B` on Uniswap V3 pool and then swap `B` to `C` on V4 pool. - Transfer `v3.tokenIn` from `msg.sender` to the `UniversalRouter` contract. - Call `UniverswalRouter.execute` with the commands `V3_SWAP_EXACT_IN`, `UNWRAP_WETH` (if `v3.tokenOut` is `WETH`) and then `V4_SWAP`. - Withdraw swapped currency to `msg.sender`. ## Test ```shell forge test --fork-url $FORK_URL --match-path test/SwapV3ToV4.test.sol -vvv ```