Combine AoC Repos

2015/day20/input

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+36000000

2015/day20/main.go

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+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Usage: day20 <number>")
+		os.Exit(1)
+	}
+	numPresents := mustAtoi(os.Args[1])
+
+	// 831600 was the lowest for part 1
+	// Part 2 won't be lower, so...
+	// 884520 for Part 2?
+	houseNum := 884500
+	k := receivedPresentsPt2(houseNum)
+	lastFound := houseNum
+	for {
+		houseNum = houseNum + 10
+		k = receivedPresentsPt2(houseNum)
+		if k >= (numPresents / 4 * 3) {
+			fmt.Print("O")
+		} else if k >= numPresents/2 {
+			fmt.Print("o")
+		} else if k >= numPresents/4 {
+			fmt.Print(".")
+		}
+		if k >= numPresents {
+			fmt.Print(" House number " + strconv.Itoa(houseNum) + " received " + strconv.Itoa(k) + " presents.")
+			fmt.Println("(" + strconv.Itoa(lastFound-houseNum) + ")")
+			lastFound = houseNum
+		}
+	}
+	/*
+		for houseNum > 40000 { //k < numPresents {
+			if houseNum%100000 == 0 {
+				fmt.Print("o")
+			} else if houseNum%1000 == 0 {
+				fmt.Print(".")
+			}
+			houseNum = houseNum - 10 //-- // = houseNum - 360
+			k = receivedPresentsPt1(houseNum)
+			if k >= numPresents {
+				fmt.Print(" House number " + strconv.Itoa(houseNum) + " received " + strconv.Itoa(k) + " presents.")
+				fmt.Println("(" + strconv.Itoa(lastFound-houseNum) + ")")
+				lastFound = houseNum
+			}
+		}
+	*/
+}
+
+func receivedPresentsPt2(house int) int {
+	var ret int
+	elves := getFactors(house)
+	for i := range elves {
+		if (house / elves[i]) <= 50 {
+			ret += elves[i] * 11
+		}
+	}
+	return ret
+}
+
+func receivedPresentsPt1(house int) int {
+	var ret int
+	elves := getFactors(house)
+	for i := range elves {
+		ret += elves[i] * 10
+	}
+	return ret
+}
+
+func getFactors(n int) []int {
+	var ret []int
+	bot := 1
+	top := n
+	for bot < n/2 {
+		if n%bot == 0 {
+			top = n / bot
+			if top == bot {
+				ret = addUnique(ret, bot)
+			} else {
+				ret = addUnique(ret, bot)
+				ret = addUnique(ret, top)
+			}
+		}
+		bot++
+	}
+	return ret
+}
+
+func addUnique(sl []int, n int) []int {
+	for i := 0; i < len(sl); i++ {
+		if sl[i] == n {
+			return sl
+		}
+	}
+	return append(sl, n)
+}
+
+func mustAtoi(s string) int {
+	var i int
+	var err error
+	if i, err = strconv.Atoi(s); err != nil {
+		fmt.Println("Tried to atoi " + s)
+		os.Exit(1)
+	}
+	return i
+}

2015/day20/problem

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+                                           Advent of Code
+
+   br0xen 40*
+
+     • [About]
+     • [Stats]
+     • [Leaderboard]
+     • [Settings]
+     • [Log out]
+
+--- Day 20: Infinite Elves and Infinite Houses ---
+
+   To keep the Elves busy, Santa has them deliver some presents by hand, door-to-door. He sends
+   them down a street with infinite houses numbered sequentially: 1, 2, 3, 4, 5, and so on.
+
+   Each Elf is assigned a number, too, and delivers presents to houses based on that number:
+
+     • The first Elf (number 1) delivers presents to every house: 1, 2, 3, 4, 5, ....
+     • The second Elf (number 2) delivers presents to every second house: 2, 4, 6, 8, 10, ....
+     • Elf number 3 delivers presents to every third house: 3, 6, 9, 12, 15, ....
+
+   There are infinitely many Elves, numbered starting with 1. Each Elf delivers presents equal to
+   ten times his or her number at each house.
+
+   So, the first nine houses on the street end up like this:
+
+ House 1 got 10 presents.
+ House 2 got 30 presents.
+ House 3 got 40 presents.
+ House 4 got 70 presents.
+ House 5 got 60 presents.
+ House 6 got 120 presents.
+ House 7 got 80 presents.
+ House 8 got 150 presents.
+ House 9 got 130 presents.
+
+   The first house gets 10 presents: it is visited only by Elf 1, which delivers 1 * 10 = 10
+   presents. The fourth house gets 70 presents, because it is visited by Elves 1, 2, and 4, for a
+   total of 10 + 20 + 40 = 70 presents.
+
+   What is the lowest house number of the house to get at least as many presents as the number in
+   your puzzle input?
+
+   Your puzzle answer was 831600.
+
+--- Part Two ---
+
+   The Elves decide they don't want to visit an infinite number of houses. Instead, each Elf will
+   stop after delivering presents to 50 houses. To make up for it, they decide to deliver presents
+   equal to eleven times their number at each house.
+
+   With these changes, what is the new lowest house number of the house to get at least as many
+   presents as the number in your puzzle input?
+
+   Your puzzle answer was 884520.
+
+   Both parts of this puzzle are complete! They provide two gold stars: **
+
+   At this point, you should return to your advent calendar and try another puzzle.
+
+   Your puzzle input was 36000000.
+
+   You can also [Shareon Twitter Google+ Reddit] this puzzle.
+
+References
+
+   Visible links
+   . http://adventofcode.com/
+   . http://adventofcode.com/about
+   . http://adventofcode.com/stats
+   . http://adventofcode.com/leaderboard
+   . http://adventofcode.com/settings
+   . http://adventofcode.com/auth/logout
+   . http://adventofcode.com/
+   . https://twitter.com/intent/tweet?text=I%27ve+completed+%22Infinite+Elves+and+Infinite+Houses%22+%2D+Day+20+%2D+Advent+of+Code&url=http%3A%2F%2Fadventofcode%2Ecom%2Fday%2F20&related=ericwastl&hashtags=AdventOfCode
+   . https://plus.google.com/share?url=http%3A%2F%2Fadventofcode%2Ecom%2Fday%2F20
+   . http://www.reddit.com/submit?url=http%3A%2F%2Fadventofcode%2Ecom%2Fday%2F20&title=I%27ve+completed+%22Infinite+Elves+and+Infinite+Houses%22+%2D+Day+20+%2D+Advent+of+Code