Solidity Library Use

ArrayContract.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "./ArrayLib.sol";

contract ArrayContract {
    using ArrayLib for uint256[]; // Import the library for use with uint256[] arrays

    uint256[] private arr; // The array to store uint256 elements

    /// @notice Adds an element to the array.
    /// @param element The element to be added.
    function addElement(uint256 element) public {
        arr.push(element);
    }

    /// @notice Calls the library to shuffle the array using a random seed.
    /// @param seed A random seed used to shuffle the array. You can use block timestamp or other data.
    function shuffleArray(uint256 seed) public {
        arr.shuffle(seed); // Calls the `shuffle` function from the ArrayLib library
    }

    /// @notice Returns the array.
    /// @return The current array of uint256 elements.
    function getArray() public view returns (uint256[] memory) {
        return arr;
    }
}

ArrayLib.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

library ArrayLib {
    /// @notice Shuffles an array of uint256 using the Fisher-Yates algorithm.
    /// @param arr The array of uint256 to be shuffled.
    /// @param seed A random seed to ensure the shuffle result is non-deterministic.
    function shuffle(uint256[] storage arr, uint256 seed) internal {
        uint256 n = arr.length;
        if (n <= 1) return;  // No need to shuffle if the array has 1 or 0 elements

        for (uint256 i = n - 1; i > 0; i--) {
            // Generate a pseudo-random index between 0 and i
            uint256 j = uint256(keccak256(abi.encode(seed, i))) % (i + 1);

            // Swap arr[i] and arr[j]
            (arr[i], arr[j]) = (arr[j], arr[i]);
        }
    }
}