AdventOfCode-ts-2023/3/3_common.ts

import { Inspect } from "../common.ts";
/* Directions */
const Directions = {
    NORTH: {
        X: 0,
        Y: -1,
    },
    SOUTH: {
        X: 0,
        Y: 1,
    },
    EAST: {
        X: 1,
        Y: 0,
    },
    WEST: {
        X: -1,
        Y: 0,
    },
    NORTH_EAST: {
        X: 1,
        Y: -1,
    },
    NORTH_WEST: {
        X: -1,
        Y: -1,
    },
    SOUTH_EAST: {
        X: 1,
        Y: 1,
    },
    SOUTH_WEST: {
        X: -1,
        Y: 1,
    },
}

/**
 * Parse the schematics to find all possible Engine Parts
 * @param {string[][]} schematicsMap A 2D grid of characters making up a schematic
 * @returns {EnginePart[]} An array of potential Engine Parts
 */
export function ParseSchematics(schematicsMap: string[][]): EnginePart[] {
    const engineParts: EnginePart[] = [];

    /** The current pointer within the schematics' 2D array */
    const schematicsPointer: Vector2 = {
        X: 0,
        Y: 0,
    };

    for(; schematicsPointer.Y < schematicsMap.length; schematicsPointer.Y++) {
        // Reset the X pointer each line
        schematicsPointer.X = 0;
        /** A line from the total schematics */
        const schematicsLine = schematicsMap[schematicsPointer.Y];

        // Create a reusable EnginePart store
        let part: EnginePart|null = null;

        for(; schematicsPointer.X < schematicsMap[schematicsPointer.Y].length; schematicsPointer.X++) {
            const char = schematicsMap[schematicsPointer.Y][schematicsPointer.X];

            // Check if the current character is a number
            if (/\d/.test(char)) {
                // Check if our EnginePart store is initialized
                if (part == null) { part = { PartNumber: 0, Coordinates: [] }; }

                if (part.PartNumber) {
                    // Concatenate the number to the existing part of the Part Number
                    part.PartNumber = Number("" + part.PartNumber + char);
                }
                else {
                    // Start the new Part Number
                    part.PartNumber = Number(char);
                }

                // Push the coordinates
                part.Coordinates.push({
                    X: schematicsPointer.X,
                    Y: schematicsPointer.Y,
                });
            }
            // If it's not
            else {
                // Check if the EnginePart store has a value
                if(part != null) {
                    // If it does, store it and empty it
                    engineParts.push(part);
                    part = null;
                }
            }
        }

        if(part !== null) {
            engineParts.push(part);
        }
    }

    return engineParts;
}

/**
 * Validates all previously parsed Engine Parts
 *
 * An Engine Part is only valid if it's connected, even diagonally, to a
 * symbol other than `.`.
 *
 * @param {EnginePart[]} potentialParts All potential Engine Parts
 * @param {string[][]} schematicsMap A 2D grid of characters making up a schematic
 * @returns {EnginePart[]} A filtered list of all valid Engine Parts
 */
export function ValidateEngineParts(potentialParts: EnginePart[], schematicsMap: string[][]): EnginePart[] {
    const validParts: EnginePart[] = [];

    for (const part of potentialParts) {
        let symbolFound = false;
        for (const point of part.Coordinates) {
            if (BordersASymbol(point, schematicsMap)) {
                symbolFound = true;
                validParts.push(part);
                break;
            }
        }
    }
    return validParts;
}

/**
* Check if a point on the schematics map borders a symbol
*
* A symbol is any character other than a digit or a period.
*
* @param point A point on the schematics map
* @param schematicsMap A 2D grid of characters making up a schematic
* @returns {boolean} Whether the point borders a symbol or not
*/
export function BordersASymbol(point: Vector2, schematicsMap: string[][]): boolean {
   // Initialize all border chars as NOPs
   let northernBorder   =  ".";
   let easternBorder    =  ".";
   let southernBorder   =  ".";
   let westernBorder    =  ".";
   let northEastBorder  =  ".";
   let northWestBorder  =  ".";
   let southEastBorder  =  ".";
   let southWestBorder  =  ".";
   // Check what borders exist
   const northExists = !!schematicsMap[point.Y + Directions.NORTH.Y];
   const southExists = !!schematicsMap[point.Y + Directions.SOUTH.Y];
   const eastExists = !!schematicsMap[point.Y][point.X + Directions.EAST.X];
   const westExists = !!schematicsMap[point.Y][point.X + Directions.WEST.X];
   // Find the border chars
   if(northExists) {
       northernBorder = schematicsMap[point.Y + Directions.NORTH.Y][point.X + Directions.NORTH.X];
       if(eastExists) {
           northEastBorder = schematicsMap[point.Y + Directions.NORTH_EAST.Y][point.X + Directions.NORTH_EAST.X];
       }
       if(westExists) {
           northWestBorder = schematicsMap[point.Y + Directions.NORTH_WEST.Y][point.X + Directions.NORTH_WEST.X];
       }
   }
   if(southExists) {
       southernBorder = schematicsMap[point.Y + Directions.SOUTH.Y][point.X + Directions.SOUTH.X];
       if(eastExists) {
           southEastBorder = schematicsMap[point.Y + Directions.SOUTH_EAST.Y][point.X + Directions.SOUTH_EAST.X];
       }
       if(westExists) {
           southWestBorder = schematicsMap[point.Y + Directions.SOUTH_WEST.Y][point.X + Directions.SOUTH_WEST.X];
       }
   }
   if (eastExists) {
       easternBorder = schematicsMap[point.Y + Directions.EAST.Y][point.X + Directions.EAST.X];
   }
   if (westExists) {
       westernBorder = schematicsMap[point.Y + Directions.WEST.Y][point.X + Directions.WEST.X];
   }
   // Combine all bordering characters into one long string
   const allBorders = northernBorder + easternBorder + southernBorder + westernBorder + northEastBorder + northWestBorder + southEastBorder + southWestBorder;

   return /[^0-9\.]/.test(allBorders);
}

/**
 * Split the schematics into a 2D grid of characters
 *
 * @param {string[]} schematics The array of lines from the schematics
 * @returns {string[][]} A 2D grid of characters
 */
export function BuildSchematicsMap(schematics: string[]): string[][] {
    return schematics.map((schematicsLine) => schematicsLine.split(''));
}

/**
 * An engine part
 */
export type EnginePart = {
    PartNumber: number,
    Coordinates: Vector2[],
};

/**
 * A gear on the schematics map
 * 
 * A gear is any `*` symbol from the schematics map that borders
 * exactly two engine part numbers.
 */
export type SchematicsGear = {
    Symbol: string,
    Coordinates: Vector2,
    GearRatio: number
};

/**
 * A position within a 2D grid
 */
export type Vector2 = {
    X: number,
    Y: number,
};