aoc/2023/day_03/solution.ts

/*

*/

import { sum } from "../../_utils";

function isDigit(char: string): boolean {
  return /^\d$/.test(char);
}

function isSymbol(char: string): boolean {
  return !isDigit(char) && char !== ".";
}

function getCharAt(
  m: string[],
  row: number,
  column: number,
  fallback: string = "."
): string {
  if (typeof m[row] !== "undefined") {
    return m[row][column] || fallback;
  } else {
    return fallback;
  }
}

export function part1_solver(lines: string[]): number {
  // approach:
  //  1. assume all numbers are invalid at first (pending)
  //  2. continuously check the pending numbers to see if they can be moved to valid (a symbol is found)
  //  3. once the iterator is out of range of a number, move it to invalid list
  let valid_part_numbers = [];

  lines.forEach((line, row) => {
    // const elements = line.split(".");
    let column = 0;
    let buffer = "";

    let is_valid = false;
    while (column <= line.length) {
      const current_char = line[column];

      if (isDigit(current_char)) {
        buffer += current_char;

        // check previous row
        const up_left = getCharAt(lines, row - 1, column - 1);
        const up_mid = getCharAt(lines, row - 1, column);
        const up_right = getCharAt(lines, row - 1, column + 1);

        const left = getCharAt(lines, row, column - 1);
        const right = getCharAt(lines, row, column + 1);

        const down_left = getCharAt(lines, row + 1, column - 1);
        const down_mid = getCharAt(lines, row + 1, column);
        const down_right = getCharAt(lines, row + 1, column + 1);

        if (!is_valid) {
          is_valid =
            isSymbol(up_left) ||
            isSymbol(up_mid) ||
            isSymbol(up_right) ||
            isSymbol(left) ||
            isSymbol(right) ||
            isSymbol(down_left) ||
            isSymbol(down_mid) ||
            isSymbol(down_right);
        }

        if (isDigit(right)) {
          column += 1;
          continue;
        } else if (isSymbol(right)) {
          valid_part_numbers.push(buffer);
          is_valid = false;
          buffer = "";
        } else {
          if (is_valid) {
            valid_part_numbers.push(buffer);
          }

          is_valid = false;
          buffer = "";
        }
      } else {
        buffer = "";
        is_valid = false;
        column += 1;
        continue;
      }

      column += 1;
    }
  });

  return valid_part_numbers
    .map((nstr) => +nstr)
    .filter((n) => !isNaN(n))
    .reduce(sum, 0);
}

/*

*/
type Element = {
  kind: "number" | "gear";
  value: string;
  position: [number, number];
};

type Gear = {
  n1: number;
  n2: number;
};

const checkColumsFor = (
  lines: string[],
  row: number,
  columns: number[]
): number[] => {
  let matched_nums = [];

  columns.forEach((column) => {
    if (isDigit(getCharAt(lines, row, column))) {
      // The target value was a digit. There are two cases:
      //  1. The digit belongs to the same number we've seen before. E.g.
      //        ...123.......
      //        ....*........
      //  2. The digit belongs to a new number on that row. E.g.
      //        ...123.456...
      //        ......*......
    } else {
      // The target value was not a digit, so ignore
    }
  });

  // columns.map(col => isDigit(getCharAt(lines, row, col))).every()
  return columns.reduce((matched_nums, column) => {
    if (isDigit(getCharAt(lines, row, column))) {
    }
  }, []);
};

const checkTopRow = (
  lines: string[],
  currentRow: number,
  currentColumn: number
): number[] => {
  const row = currentRow - 1;
  const column = currentColumn;
  let adjacent_nums = [];

  const up_left = getCharAt(lines, row, currentColumn - 1);
  const up_mid = getCharAt(lines, row, currentColumn);
  const up_right = getCharAt(lines, row, currentColumn + 1);

  if (isDigit(up_left) || isDigit(up_mid) || isDigit(up_right)) {
    console.log("found on prev row");
    // get all the nums from the previous row
    const nums = (lines[row - 1] || "")
      .split(".")
      .filter((s) => s.length > 0)
      .map((s) =>
        s
          .split("")
          .filter((c) => isDigit(c))
          .join("")
      );

    // figure out which num overlaps this gear
    const res1 = nums.find((n) => {
      const foundNumIndex = lines[row - 1].indexOf(n);
      const lastDigit = foundNumIndex + n.length - 1;

      console.log(JSON.stringify({ foundNumIndex, lastDigit, column }));
      return (
        foundNumIndex === column - 1 ||
        foundNumIndex === column ||
        foundNumIndex === column + 1 ||
        lastDigit === column - 1 ||
        lastDigit === column ||
        lastDigit === column + 1 ||
        (column - 1 >= foundNumIndex && column + 1 <= lastDigit)
      );
    });

    if (res1) {
      adjacent_nums.push(res1);

      const res2 = nums.slice(nums.indexOf(res1)).find((n) => {
        const foundNumIndex = lines[row - 1].indexOf(n);
        const lastDigit = foundNumIndex + n.length - 1;

        console.log(JSON.stringify({ foundNumIndex, lastDigit, column }));
        return (
          foundNumIndex === column - 1 ||
          foundNumIndex === column ||
          foundNumIndex === column + 1 ||
          lastDigit === column - 1 ||
          lastDigit === column ||
          lastDigit === column + 1 ||
          (column - 1 >= foundNumIndex && column + 1 <= lastDigit)
        );
      });

      if (res2) {
        adjacent_nums.push(res2);
      }

      console.log(
        "res is " +
          JSON.stringify({
            res1,
            res2,
            nums,
            last: lines[row - 1],
            column,
          })
      );
    }
  }

  return adjacent_nums;
};

const checkCurrentRow = (
  lines: string[],
  currentRow: number,
  currentColumn: number
): number[] => {
  const row = currentRow - 1;
  const column = currentColumn;
  let adjacent_nums = [];

  const left = getCharAt(lines, row, column - 1);
  const right = getCharAt(lines, row, column + 1);

  if (isDigit(left) || isDigit(right)) {
    console.log("found on this row");
    // get all the nums from this row
    const nums = lines[row]
      .split(".")
      .filter((s) => s.length > 0)
      .map((s) =>
        s
          .split("")
          .filter((c) => isDigit(c))
          .join("")
      );

    // figure out which num overlaps this gear
    const res1 = nums.find((n) => {
      const foundNumIndex = lines[row].indexOf(n);
      const lastDigit = foundNumIndex + n.length - 1;

      return (
        foundNumIndex === column - 1 ||
        foundNumIndex === column ||
        foundNumIndex === column + 1 ||
        lastDigit === column - 1 ||
        lastDigit === column ||
        lastDigit === column + 1 ||
        (column - 1 >= foundNumIndex && column + 1 <= lastDigit)
      );
    });

    if (res1) {
      adjacent_nums.push(res1);

      const res2 = nums.find((n) => {
        const foundNumIndex = lines[row].indexOf(n);
        const lastDigit = foundNumIndex + n.length - 1;

        return (
          foundNumIndex === column - 1 ||
          foundNumIndex === column ||
          foundNumIndex === column + 1 ||
          lastDigit === column - 1 ||
          lastDigit === column ||
          lastDigit === column + 1 ||
          (column - 1 >= foundNumIndex && column + 1 <= lastDigit)
        );
      });

      if (res2) {
        adjacent_nums.push(res2);
      }
    }
  }

  return adjacent_nums;
};

const checkBottomRow = (
  lines: string[],
  currentRow: number,
  currentColumn: number
): number[] => {
  const row = currentRow - 1;
  const column = currentColumn;
  let adjacent_nums = [];

  const down_left = getCharAt(lines, row + 1, column - 1);
  const down_mid = getCharAt(lines, row + 1, column);
  const down_right = getCharAt(lines, row + 1, column + 1);

  if (isDigit(down_left) || isDigit(down_mid) || isDigit(down_right)) {
    console.log("found on next row");
    // get all the nums from the next row
    const nums = lines[row + 1]
      .split(".")
      .filter((s) => s.length > 0)
      .map((s) =>
        s
          .split("")
          .filter((c) => isDigit(c))
          .join("")
      );

    // figure out which num overlaps this gear
    const res1 = nums.find((n) => {
      // [6 7 8 9]
      // [0 1 2 3]
      const foundNumIndex = lines[row + 1].indexOf(n);
      const lastDigitIndex = foundNumIndex + n.length - 1;

      return (
        foundNumIndex === column - 1 ||
        foundNumIndex === column ||
        foundNumIndex === column + 1 ||
        lastDigitIndex === column - 1 ||
        lastDigitIndex === column ||
        lastDigitIndex === column + 1 ||
        (column - 1 >= foundNumIndex && column + 1 <= lastDigitIndex)
      );
    });

    if (res1) {
      adjacent_nums.push(res1);

      const res2 = nums.find((n) => {
        // [6 7 8 9]
        // [0 1 2 3]
        const foundNumIndex = lines[row + 1].indexOf(n);
        const lastDigitIndex = foundNumIndex + n.length - 1;

        return (
          foundNumIndex === column - 1 ||
          foundNumIndex === column ||
          foundNumIndex === column + 1 ||
          lastDigitIndex === column - 1 ||
          lastDigitIndex === column ||
          lastDigitIndex === column + 1 ||
          (column - 1 >= foundNumIndex && column + 1 <= lastDigitIndex)
        );
      });

      if (res2) {
        adjacent_nums.push(res2);
      }
    }
  }

  return adjacent_nums;
};

export function part2_solver(lines: string[]): number {
  let gears: Gear[] = [];

  lines.forEach((line, row) => {
    let column = 0;
    let adjacent_nums = [];

    while (column <= line.length) {
      const current_char = line[column];

      if (current_char === "*") {
        const top_nums = checkTopRow(lines, row, column);
        adjacent_nums.push(top_nums);

        const current_nums = checkCurrentRow(lines, row, column);
        adjacent_nums.push(current_nums);

        const bottom_nums = checkBottomRow(lines, row, column);
        adjacent_nums.push(bottom_nums);

        console.log(JSON.stringify({ adjacent_nums }));

        if (adjacent_nums.length === 2) {
          console.log("found a gear!");
          gears.push({ n1: +adjacent_nums[0], n2: +adjacent_nums[1] });
        } else {
          adjacent_nums = [];
        }
      } else {
        adjacent_nums = [];
        column += 1;
        continue;
      }

      column += 1;
    }
  });

  return gears
    .map((g) => g.n1 * g.n2)
    .filter((n) => !isNaN(n))
    .reduce(sum, 0);
}