gift-selection.js

const fs = require('fs');

fs.readFile('input', 'utf8', (err, contents) => {
	// console.log(contents);
	const data = parseData(contents);
	data.prices.sort((a, b) => a > b);

	const result = solve(data.prices, data.m);
	console.log(result);
});

const solve = (prices, targetPrice) => {
	let result = null;
	for (let i = 0; i < prices.length - 1; i++) {
		let currentResult = compare(prices[i], targetPrice, prices.slice(i));
		// console.log(currentResult);
		if (currentResult) {
			if (!result || currentResult.diff < result.diff) {
				result = currentResult;
			}

			// console.log('result: ', result);
		}
	}

	return result;
};

const compare = (basePrice, targetPrice, prices) => {
	if (prices.length === 1) {
		if (basePrice + prices[0] === targetPrice) {
			return {
				diff: prices[0] - basePrice,
				left: basePrice,
				right: prices[0],
			};
		} else {
			return null;
		}
	} else if (basePrice + prices[0] === targetPrice) {
		return {
			diff: prices[0] - basePrice,
			left: basePrice,
			right: prices[0],
		};
	} else {
		return compare(basePrice, targetPrice, prices.slice(1));
	}
};

const parseData = contents => {
	let result = {};
	try {
		const splitContents = contents.split(/\r?\n/);
		result.n = parseInt(splitContents[0]);
		result.prices = splitContents[1].split(' ').map(x => parseInt(x));
		result.m = parseInt(splitContents[2]);
	} catch (e) {
		console.log('error: ', e);
	}

	return result;
};