randomTokenSelector Untested

randomTokenSelector.sol

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

/*
This code is untested, feel free to use it, but do so at your own risk
*/

contract Random {

    uint256[] tokens = new uint256[](100);

    constructor(){
        for(uint256 i; i < 100; i++){
            tokens[i] = i;
        }
    }

    function random() public returns (uint256){
        require(tokens.length > 0, "Array is empty");

        // index of the last value in the tokens array
        uint256 lastIndex = tokens.length - 1;

        // down to the last array value so we can pop it and we are all done
        if(lastIndex == 0){
            uint256 tokenId = tokens[0];
            tokens.pop();
            return tokenId;
        }

        // pick a random number from 0 to the length of the tokens array
        uint256 randIndex = uint256(keccak256(abi.encode(block.timestamp, lastIndex))) % lastIndex;

        // use the random number to pull a value from the token array at the randNum index
        uint256 tokenId = tokens[randIndex];


        if(randIndex == lastIndex){
            // if the randNum == last index in tokens, remove the last array value
            tokens.pop();
        } else {
            // randNum was in the middle of the array so we need to do some cleanup
            // grab the last value from the array
            uint256 lastValue = tokens[lastIndex];
            // inject the last value into the at index value of randIndex
            tokens[randIndex] = lastValue;
            // remove last value from the array
            tokens.pop();
        }

        return tokenId;
    }
}

This code is untested, feel free to use it, but do so at your own risk