— Day 1: Report Repair —

Fleur Kelpin Dec 1, 2020

library(tidyverse)
input <- read.csv("day01.txt")[, 1]

Part 1

Find the two entries that sum to 2020 and then multiply those two numbers together.

input %>%
  c(., 2020 - .) %>%
  .[duplicated(.)] %>%
  prod()

## [1] 786811

What is the product of the three entries that sum to 2020?

input %>%
  combn(3) %>%
  .[,colSums(.) == 2020] %>%
  prod()

## [1] 199068980