Nice. Software developer, gamer, occasionally 3d printing, coffee lover.

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  • 637 Comments
Joined 2 years ago
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Cake day: July 1st, 2023

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  • Javascript

    I generally like trying the brute force approach first (though in the latter days it just wastes time). After exhausting 32GB of RAM I changed approaches.

    Admittedly I don’t really understand these algorithms as well as I would like, and I also will admit I inadvertently was LLM assisted :(. When I was trying to figure out what algo I should use and the AI summary in Google’s search spoiled me. But I did learn alot.

    One interesting observation, unrelated to the solution itself, is the solutions runs about 30% faster in Firefox than it does via Node (25.2.1 and 24.11.1) on my machine.

    Code
    const input = require('fs').readFileSync('input-day9.txt', 'utf-8');
    
    /** @type {Array<[number, number]} */
    const points = input.split("\n").map(r => r.split(',').map(v => parseInt(v, 10)));
    
    let largest = 0;
    let largestInside = 0;
    for (const [startX, startY] of points) {
        for (const [nextX, nextY] of points) {
            if (startX === nextX && startY === nextY) continue;
    
            const minX = Math.min(startX, nextX);
            const maxX = Math.max(startX, nextX);
            const minY = Math.min(startY, nextY);
            const maxY = Math.max(startY, nextY);
    
            const area = (maxX - minX + 1) * (maxY - minY + 1);
            if (area > largest) {
                largest = area;
            }
    
            if (area <= largestInside) continue;
    
            // center point check, ala https://en.wikipedia.org/wiki/Even%E2%80%93odd_rule
            const centerX = (minX + maxX) / 2;
            const centerY = (minY + maxY) / 2;
            let inside = false;
            for (const [i, [aX, aY]] of points.entries()) {
                const [bX, bY] = points[i - 1] ?? points[points.length - 1];
                if (centerX === aX && centerY === aY) {
                    inside = true;
                    break;
                }
                if ((aY > centerY) !== (bY > centerY)) {
                    const slope = (centerX - aX) * (bY - aY) - (bX - aX) * (centerY - aY);
                    if (slope === 0) {
                        inside = true;
                        break;
                    }
                    if ((slope < 0) !== (bY < aY)) {
                        inside = !inside;
                    }
                }
            }
    
            if (!inside) continue;
    
            // check for edge intersections, ala https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection
            let intersects = false;
            for (const [i, [aX, aY]] of points.entries()) {
                const [bX, bY] = points[i - 1] ?? points[points.length - 1];
    
                if (aX === bX) {
                    if (aX > minX && aX < maxX) {
                        const wallMinY = Math.min(aY, bY);
                        const wallMaxY = Math.max(aY, bY);
    
                        if (Math.max(minY, wallMinY) < Math.min(maxY, wallMaxY)) {
                            intersects = true;
                            break;
                        }
                    }
                } else if (aY === bY) {
                    if (aY > minY && aY < maxY) {
                        const wallMinX = Math.min(aX, bX);
                        const wallMaxX = Math.max(aX, bX);
    
                        if (Math.max(minX, wallMinX) < Math.min(maxX, wallMaxX)) {
                            intersects = true;
                            break;
                        }
                    }
                }
            }
    
            if (intersects) continue;
    
            if (area > largestInside) {
                largestInside = area;
            }
        }
    }
    
    console.log(`Part 1 Answer: ${largest}`);
    console.log(`Part 2 Answer: ${largestInside}`);
    





  • Javascript

    Short and sweet. Basically just handle all the range overlaps for part 2 and then do basic subtraction to get the answer.

    spoiler
    const input = require('fs').readFileSync('input-day5.txt', 'utf-8');
    
    /** @typedef {[number, number]} Range */
    
    /** @type {[Range[], number[]]} */
    const [freshRanges, availableIngredients] = input.split("\n\n").map(l => l.split("\n")).map((l, i) => (i === 1) ? l.map(v => parseInt(v, 10)) : l.map(v => v.split('-').map(vv => parseInt(vv, 10))));
    
    
    let freshOnHand = 0;
    
    for (const ingredient of availableIngredients) {
        for (const [start, stop] of freshRanges) {
            if (ingredient >= start && ingredient <= stop) {
                freshOnHand += 1;
                break;
            }
        }
    }
    
    console.log(`Part 1 Answer: ${freshOnHand}`);
    
    const sortedRanges = [...freshRanges].sort((a, b) => a[0] - b[0]);
    
    const mergedRanges = [];
    let current = sortedRanges[0];
    
    for (let i = 1; i < sortedRanges.length; i++) {
        const [nextStart, nextEnd] = sortedRanges[i];
        
        if (nextStart <= current[1] + 1) {
            current = [current[0], Math.max(current[1], nextEnd)];
        } else {
            mergedRanges.push(current);
            current = [nextStart, nextEnd];
        }
    }
    
    mergedRanges.push(current);
    
    const freshIngredientCount = mergedRanges.reduce((acc, [start, stop]) => acc + ((stop + 1) - start), 0)
    
    console.log(`Part 2 Answer: ${freshIngredientCount}`);
    


  • Javascript

    After smashing out a functional version in 20 minutes, I converted it into a OOP approach for a more appealing solution.

    Solution
    const input = require('fs').readFileSync('input-day4.txt', 'utf-8');
    
    class PrintingDepartmentMap {
        /** @param {string} input */
        constructor(input) {
            /** @type {number[][]} */
            this.map = input.split("\n").map(r => r.split('').map(v => v === '@' ? 1 : 0));
        }
    
        /**
         * @param {number} x
         * @param {number} y
         * @returns {number} the value of that tile, or -1 if invalid
         */
        getCoord(x, y) {
            if (x < 0 || y < 0 || x >= this.map[0].length || y >= this.map.length) {
                return -1;
            }
            return this.map[y][x];
        }
    
        /**
         * @param {number} x
         * @param {number} y
         * @returns {number} the number of adjacent tiles that are >= 1
         */
        countAdjacent(x, y) {
            return [
                // top-left
                this.getCoord(x - 1, y - 1) >= 1,
                // top
                this.getCoord(x, y - 1) >= 1,
                // top-right
                this.getCoord(x + 1, y - 1) >= 1,
                // right
                this.getCoord(x + 1, y) >= 1,
                // bottom-right
                this.getCoord(x + 1, y + 1) >= 1,
                // bottom
                this.getCoord(x, y + 1) >= 1,
                // bottom-left
                this.getCoord(x - 1, y + 1) >= 1,
                // left
                this.getCoord(x - 1, y) >= 1
            ].reduce((acc, v) => !!v ? acc + 1 : acc, 0);
        }
    
        /**
         * transform in place the map replacing any rolls (1) with (2) if they are accessible
         * @returns {PrintingDepartmentMap}
         */
        markAccessable() {
            for (let y = 0; y < this.map.length; y += 1) {
                for (let x = 0; x < this.map[0].length; x += 1) {
                    if (this.map[y][x] < 1) continue;
                    if (this.countAdjacent(x, y) < 4) {
                        this.map[y][x] = 2;
                    }
    
                }
            }
            return this;
        }
    
        /** @returns {number} the number of removed rolls */
        removeAccessable() {
            let removed = 0;
            for (let y = 0; y < this.map.length; y += 1) {
                for (let x = 0; x < this.map[0].length; x += 1) {
                    if (this.map[y][x] === 2) {
                        removed += 1;
                        this.map[y][x] = 0;
                    }
                }
            }
            return removed;
        }
    }
    
    const map = new PrintingDepartmentMap(input);
    
    let removed = 0;
    while (true) {
        const justRemoved = map.markAccessable().removeAccessable();
        if (removed === 0) {
            console.log(`Part 1 Answer: ${justRemoved}`);
        }
        if (justRemoved === 0) break;
        removed += justRemoved;
    }
    
    console.log(`Part 2 Answer: ${removed}`);
    



  • Javascript

    More bruteforcing! There are probably better ways to do this but I’m happy enough with this lol.

    Solution

    You can replace the require(‘fs’) on the first line with the input and run it in your browser console as well.

    const input = require('fs').readFileSync('input-day2.txt', 'utf-8');
    
    let idsPart1 = [];
    let idsPart2 = [];
    
    input.split(',').forEach(range => {
        const [start, end] = range.split('-').map(v => parseInt(v, 10));
        let cursor = start;
    
        while (cursor <= end) {
            const cursorString = cursor.toString(10);
    
            // part 1 check
            let halfLength = Math.floor(cursorString.length / 2);
            let left = cursorString.slice(0, halfLength);
            let right = cursorString.slice(halfLength, cursorString.length);
            if (left === right) {
                idsPart1.push(cursor);
            }
    
            // part 2 check
            let sequenceLength = 1;
            while (sequenceLength <= halfLength) {
                const sequence = cursorString.slice(0, sequenceLength);
                let builtString = sequence;
                while (builtString.length < cursorString.length) {
                    builtString = `${builtString}${sequence}`;
                }
                if (builtString === cursorString) {
                    idsPart2.push(cursor);
                    break;
                }
    
                sequenceLength += 1;
            }
    
            cursor += 1;
        }
    })
    
    const answer1 = idsPart1.flat().reduce((acc, cur) => acc += cur, 0);
    const answer2 = idsPart2.flat().reduce((acc, cur) => acc += cur, 0);
    
    console.log(`Part 1 Answer: ${answer1}`);
    console.log(`Part 2 Answer: ${answer2}`);
    

  • A straightforward day 1 for a Javascript / NodeJS solution.

    Poorly Optimized JS Solution
    let position = 50;
    let answer1 = 0;
    let answer2 = 0;
    
    const sequence = require('fs').readFileSync('input-day1.txt', 'utf-8');
    
    sequence.split('\n').forEach(instruction => {
        const turn = instruction.charAt(0);
        let distance = parseInt(instruction.slice(1), 10);
    
        while (distance > 0) {
            distance -= 1;
    
            if (turn === 'L') {
                position -= 1;
            } else if (turn === 'R') {
                position += 1;
            }
    
            if (position >= 100) {
                position -= 100;
            } else if (position < 0) {
                position += 100;
            }
    
            if (position === 0) {
                answer2 += 1;
            }
        }
    
        if (position === 0) {
            answer1 += 1;
        }
    });
    
    console.log(`Part 1 Answer: ${answer1}`);
    console.log(`Part 2 Answer: ${answer2}`);