Advent of Code 2020 Solution Megathread - Day 1: Report Repair

  def part1() do
    numbers = Enum.map(@numbers, &String.to_integer(&1))

    [res | _] = for x <- numbers,
      y <- numbers,
      x + y == 2020,
      do: x * y

    res
  end

  def part2() do
    numbers = Enum.map(@numbers, &String.to_integer(&1))

    [res | _] = for x <- numbers,
      y <- numbers,
      z <- numbers,
      x + y + z == 2020,
      do: x * y * z

    res
  end

SELECT
       a1.num*a2.num*a3.num
FROM
       day1 a1
     , day1 a2
     , day1 a3
WHERE
       a1.num + a2.num + a3.num = 2020
LIMIT 1

fn sums_to<'a>(
    sum: &'_ usize,
    curr: &'a usize,
    rest: &'a [usize],
) -> Option<(&'a usize, &'a usize)> {
    if rest.len() == 0 {
        return Option::None;
    }
    for re in rest {
        if re + curr == *sum {
            return Option::Some((curr, re));
        }
    }
    sums_to(sum, &rest[0], &rest[1..])
}

fn tri_sums_to<'a>(
    sum: &'_ usize,
    x: &'a usize,
    rest: &'a [usize],
) -> Option<(&'a usize, &'a usize, &'a usize)> {
    if rest.len() == 0 {
        return Option::None;
    }
    if x < sum {
        let sub_sum = *sum - x;
        for i in 0..(rest.len() - 1) {
            if let Some((a, b)) = sums_to(&sub_sum, &rest[i], &rest[i + 1..]) {
                return Option::Some((x, a, b));
            }
        }
    }
    tri_sums_to(sum, &rest[0], &rest[1..])
}

async fn day1_1() -> Result<usize> {
    let input = input_to_vec(1).await?;
    let (v1, v2) = sums_to(&2020, &input[0], &input[1..]).unwrap();
    Ok(v1 * v2)
}

async fn day1_2() -> Result<usize> {
    let input = input_to_vec(1).await?;
    let (v1, v2, v3) = tri_sums_to(&2020, &input[0], &input[1..]).unwrap();
    Ok(v1 * v2 * v3)
}

def part_one(nums, set_nums):
    for num in nums:
        if 2020 - num in set_nums:
            return num * (2020 - num)


def part_two(nums, set_nums):
    for num in nums:
        for num2 in nums:
            if (2020 - num - num2) in set_nums:
                return num * (2020 - num - num2) * num2


with open("input.txt") as _file:
    nums = [int(line) for line in _file]
    set_nums = set(nums)

    print("Part 1", part_one(nums, set_nums))
    print("Part 2", part_two(nums, set_nums))

with open("input.txt") as f:
    l = [int(x.strip()) for x in f]

for i, n1 in enumerate(l):
    for j, n2 in enumerate(l[i+1:]):
        if n1 + n2 == 2020:
            part1 = n1 * n2
        for n3 in l[i+j+1:]:
            if n1 + n2 + n3 == 2020:
                part2 = n1 * n2 * n3

print(part1)
print(part2)

/// Day 1: Report Repair
/// 
/// My expense report for my trip is messed up and entries need
/// adjusting.

#include <stdio.h>
#include <stdlib.h>

/// Parse the input file, which contains one positive integer per line.
int* parse(const char* filename, size_t* count) {
  FILE *fp;

  fp = fopen(filename, "r");
  if (fp == NULL) {
    printf("Could not open input file.\n");
    exit(EXIT_FAILURE);
  }

  // Count how many we need
  size_t lines = 0;
  while (!feof(fp)) {
    if (fgetc(fp) == '\n') lines++;
  }
  lines++;  // The last line has no newline, but we should count it.
  rewind(fp);

  int* entries = malloc(sizeof(int)*lines);

  char buff[5];  // No numbers greater than 4 digits
  for (size_t i = 0; i < lines; i++) {
    fgets(buff, 6, fp);
    entries[i] = atoi(buff);
  }
  fclose(fp);

  *count = lines;
  return entries;
}

/// Part 1 finds the two entries that add up to 2020 exactly and returns
/// their product, or -1 if none are found.
int part1(int* entries, size_t count) {
  for (size_t i = 0; i < count; i++) {
    for (size_t j = i + 1; j < count; j++) {
      if (entries[i] + entries[j] == 2020) {
        return entries[i] * entries[j];
      }
    }
  }
  return -1;
}

/// Part 2 is the same as Part 1, but we're looking for a trio of numbers
/// that sum up to 2020.  Returns their product or -1 if no trio is found.
int part2(int* entries, size_t count) {
  for (size_t i = 0; i < count; i++) {
    for (size_t j = i + 1; j < count; j++) {
      for (size_t k = j + 1; k < count; k++) {
        if (entries[i] + entries[j] + entries[k] == 2020) {
          return entries[i] * entries[j] * entries[k];
        }
      }
    }
  }
  return -1;
}

int main() {
  size_t count;
  int* entries = parse("day1/day1.txt", &count);
  printf("The 2020 pair product is: %d\n", part1(entries, count));
  printf("The 2020 triplet product is: %d\n", part2(entries, count));
  return EXIT_SUCCESS;
}

const input = JSON.parse(require('fs').readFileSync('1a.json', 'utf-8'));

// sort ascending
input.sort((a, b) => a - b);


function go(c, tgt) {
  // tgt is the target sum we're aiming for
  // a is an index which moves through the array, 
  // b is ahead of a but retreats to maintain a sum <= to target.

  for (let a = c, b = input.length - 1; a < input.length; a++) {
    let { [a]: av, [b]: bv } = input;
    while (av + bv > tgt && b >= a) bv = input[--b];
    if (av + bv == tgt) return { a, b };
  }
}

let res;
// Part 1
(res = go(0, 2020)) &&
  console.log({
    part: 1,
    sum: input[res.a] + input[res.b],
    prod: input[res.a] * input[res.b],
  });

// Part 2
for (const c in input)
  (res = go(c, 2020 - input[c])) &&
    console.log({
      part: 2,
      sum: input[res.a] + input[res.b] + input[c],
      prod: input[res.a] * input[res.b] * input[c],
    });

for (a,b) in itertools.combinations([int(n) for n in open('input')], 2): 
    if a+b == 2020: 
        print(a*b) 

   IDENTIFICATION DIVISION.
   PROGRAM-ID. Advent-of-Code-2020-day-1-part-2.
   AUTHOR. ANNA KOSIERADZKA.

   ENVIRONMENT DIVISION.
   INPUT-OUTPUT SECTION.
   FILE-CONTROL.
       SELECT INPUTFILE ASSIGN TO "d1.input"
       ORGANIZATION IS LINE SEQUENTIAL.

   DATA DIVISION.
   FILE SECTION.
     FD INPUTFILE.
     01 INPUTRECORD PIC 9(4).
   WORKING-STORAGE SECTION.
     01 FILE-STATUS PIC 9 VALUE 0.
     01 WS-ARRAY-LEN PIC 9(3) VALUE 200.
     01 WS-ARRAY PIC 9(4) OCCURS 0 to 200 DEPENDING ON WS-ARRAY-LEN.
     01 WS-SUM PIC 9(4).
     01 WS-PRODUCT-1 PIC 9(8).
     01 WS-PRODUCT-2 PIC 9(12).

   LOCAL-STORAGE SECTION.
     01 I USAGE UNSIGNED-INT VALUE 1.
     01 J USAGE UNSIGNED-INT VALUE 1.
     01 K USAGE UNSIGNED-INT VALUE 1.

   PROCEDURE DIVISION.
   001-MAIN.
        OPEN INPUT INPUTFILE.
        PERFORM 002-READ UNTIL FILE-STATUS = 1.
        CLOSE INPUTFILE.
        PERFORM 004-LOOP.
        STOP RUN.

   002-READ.
        READ INPUTFILE
            AT END MOVE 1 TO FILE-STATUS
            NOT AT END PERFORM 003-WRITE-TO-TABLE
        END-READ.

   003-WRITE-TO-TABLE.
       COMPUTE WS-ARRAY(I) = INPUTRECORD
       ADD 1 to I.

   004-LOOP.
       PERFORM VARYING I FROM 1 BY 1 UNTIL I > WS-ARRAY-LEN
       AFTER J FROM 1 BY 1 UNTIL J > WS-ARRAY-LEN
       AFTER K FROM 1 BY 1 UNTIL K > WS-ARRAY-LEN
         ADD WS-ARRAY(I) WS-ARRAY(J) WS-ARRAY(K) GIVING WS-SUM
         IF WS-SUM = 2020 THEN
           MULTIPLY WS-ARRAY(I) BY WS-ARRAY(J) GIVING WS-PRODUCT-1 
           MULTIPLY WS-PRODUCT-1 BY WS-ARRAY(K) GIVING WS-PRODUCT-2
           DISPLAY WS-PRODUCT-2
           EXIT PERFORM
         END-IF
       END-PERFORM.

class AdventAccount

  def initialize(expenses, factor=2)
    @expenses = expenses
    @factor = factor
  end

  def perform
    filter_big_nums
    winning_number(do_si_do)
  end

  private

  def filter_big_nums
    @expenses.reject! { |expense| expense >= 2020 }
  end

  def find_your_partner
    @expenses.combination(@factor).to_a()
  end

  def winning_set(group)
    group.sum == 2020
  end

  def do_si_do
    find_your_partner.each do |group|
      puts "Checking group #{group}"
      return group if winning_set(group)
    end
  end

  def winning_number(group)
    puts "the winning number is #{group.reduce(:*)}"
  end

end

puts "Starting up the Advent Account checker"
puts "Submit expenses now:"
expenses = gets.chomp.split(",").map(&:to_i)
puts "Thanks! Now, what factor should we search the expenses with?"
factor = gets.chomp.to_i
test = AdventAccount.new(expenses, factor)

test.perform

def part_one(nums, target):
    seen = set()
    possible = False
    for num in nums:
        required = target - num
        if required in seen:
            possible = True
            break
        seen.add(num)
    if possible:
        return num, required
    return -1

def part_two(nums, target):
    seen = set()
    possible = False
    for num in nums:
        for num_2 in nums:
            req_num = target - num - num_2
            if req_num in seen:
                possible = True
                break
            seen.add(num_2)
        else:
            continue
        break
    if possible:
        return num, num_2, req_num
    return -1

with open("input.txt") as input:
    nums = [int(line) for line in input]
    res = part_one(nums, 2020)
    if res != -1:
        x,y = res
        print(f"Part 1 numbers are {x}, {y}, product is {x*y}")
    else:
        print(f"Part 1 cannot be solved from this dataset")

    res_2 = part_two(nums, 2020)
    if res_2 != -1:
        x,y,z = res_2
        print(f"Part 2 numbers are {x}, {y}, {z} product is {x*y*z}")
    else:
        print(f"Part 2 cannot be solved from this dataset")

# PART01 - Find the two number that sum == T then multiply each other
# PART02 - Find the triplets that sum == T  then multiply each other

from itertools import combinations
from math import prod

I = list([int(x) for x in open('input.txt', 'r').readlines()])
T = 2020

# PART01
I2 = [x for x in combinations(I,2) if sum(x) == T]
R_P01 = prod([x for x in I2[0]])

# PART02
I3 = [x for x in combinations(I,3) if sum(x) == T]
R_P02 = prod([x for x in I3[0]])

    if let Some((a, b, c)) = input.iter().find_map(|a| {
        if let Some((b, c)) = input.iter().find_map(|b| {
            if let Some(c) = input.iter().find(|c| a + b + *c == 2020) {
                Some((b, c))
            } else {
                None
            }
        }) {
            Some((a, b, c))
        } else {
            None
        }
    }) {
        println!("A: {}, B: {}, C: {} result: {}", a, b, c, a * b * c);
    } else {
        println!("Could not find numbers fullfilling the requirement")
    }

    match input.iter().find_map(|a| {
        input.iter().find_map(|b| {
            input.iter().find_map(|c| {
                if a + b + c == 2020 {
                    Some((a, b, c))
                } else {
                    None
                }
            })
        })
    }) {
        Some((a, b, c)) => println!("A: {}, B: {}, C: {} result: {}", a, b, c, a * b * c),
        None => println!("Could not find numbers fullfilling the requirement"),
    }