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Solved Day 20 part 2 (2015) - Infinite Elves and Infinite Houses

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src/main/java/com/sbaars/adventofcode/year15/days
- Day20.java

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`‎src/main/java/com/sbaars/adventofcode/year15/days/Day20.java‎`

Lines changed: 14 additions & 6 deletions

Original file line number	Diff line number	Diff line change
`@@ -16,7 +16,7 @@ public Day20() {`
`16`	`16`	`public static void main(String[] args) {`
`17`	`17`	`Day20 day = new Day20();`
`18`	`18`	`day.printParts();`
`19`		`- new com.sbaars.adventofcode.network.Submit().submit(day.part1(), 2015, 20, 1);`
	`19`	`+ new com.sbaars.adventofcode.network.Submit().submit(day.part2(), 2015, 20, 2);`
`20`	`20`	`}`
`21`	`21`
`22`	`22`	`@Override`
`@@ -30,7 +30,18 @@ public Object part1() {`
`30`	`30`
`31`	`31`	`@Override`
`32`	`32`	`public Object part2() {`
`33`		`- return 0; // Implement in next part`
	`33`	`+ int houseNumber = 1;`
	`34`	`+ while (getPresentsForHousePart2(houseNumber) < TARGET_PRESENTS) {`
	`35`	`+ houseNumber++;`
	`36`	`+ }`
	`37`	`+ return houseNumber;`
	`38`	`+ }`
	`39`	`+`
	`40`	`+ private int getPresentsForHousePart2(int houseNumber) {`
	`41`	`+ return getDivisors(houseNumber).stream()`
	`42`	`+ .filter(elf -> houseNumber / elf <= 50) // Each Elf only visits 50 houses`
	`43`	`+ .mapToInt(elf -> elf * 11) // Each Elf delivers 11 presents`
	`44`	`+ .sum();`
`34`	`45`	`}`
`35`	`46`
`36`	`47`	`private int getPresentsForHouse(int houseNumber) {`
`@@ -41,15 +52,12 @@ private int getPresentsForHouse(int houseNumber) {`
`41`	`52`
`42`	`53`	`private Set<Integer> getDivisors(int number) {`
`43`	`54`	`Set<Integer> divisors = new HashSet<>();`
`44`		`- int sqrt = (int) Math.sqrt(number);`
`45`		`-`
`46`		`- for (int i = 1; i <= sqrt; i++) {`
	`55`	`+ for (int i = 1; i <= Math.sqrt(number); i++) {`
`47`	`56`	`if (number % i == 0) {`
`48`	`57`	`divisors.add(i);`
`49`	`58`	`divisors.add(number / i);`
`50`	`59`	`}`
`51`	`60`	`}`
`52`		`-`
`53`	`61`	`return divisors;`
`54`	`62`	`}`
`55`	`63`	`}`

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`‎src/main/java/com/sbaars/adventofcode/year15/days/Day20.java‎`

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