Who needs mappings? I’ve created a contract that can store key/value pairs using just an array.

pragma solidity ^0.4.21;

contract MappingChallenge {
    bool public isComplete;
    uint256[] map;

    function set(uint256 key, uint256 value) public {
        // Expand dynamic array as needed
        if (map.length <= key) {
            map.length = key + 1;

        map[key] = value;

    function get(uint256 key) public view returns (uint256) {
        return map[key];

Enjoy this inspirational music while you work: Map To My Heart.