Advent of Code: Day 25

2015-12-25

Part 1: Take the relation:

F(n) = \left\{\begin{matrix} 20151225 & \textrm{if}\ n = 1 \\ 252533F(n-1) \mod 33554393 & \textrm{otherwise} \end{matrix}\right.

Arrange the values according to Cantor's diagonal argument. Find the value at a specific cell.

Advent of Code: Day 24

2015-12-24

Source

Part 1: Split a list of integers into three groups of equal sum. Find the grouping such that the smallest group has the least items, breaking ties by the smallest product for that group.

Advent of Code: Day 23

2015-12-23

Source

Part 1: Create a simple virtual machine with two registers (a and b, non-negative integers) and six instructions:

hlf (a|b) - divide the given register by half, round down
tpl (a|b) - triple the given register
inc (a|b) - add 1 to the given register
jmp [+-]\d+ - jump forward/backwards by the given number of instructions
jie (a|b), [+-]\d+ - if the given register is even, jump
jio (a|b), [+-]\d+ - if the given register equals one, jump

Advent of Code: Day 22

2015-12-22

Source

Part 1: Simulate an RPG mage battle; finding the winning solution using the least mana. See the original writeup for more details.

Advent of Code: Day 21

2015-12-21

Source

Part 1: Given a shop full of weapons (buy exactly one), armor (buy zero or one), and rings (buy 0, 1, or 2), determine the set of items that will defeat a given enemy for the minimum cost (see the original writeup for more details).

Advent of Code: Day 20

2015-12-20

Source

Part 1: P(n) is defined such that for each number i, add 10i to any number divisible by i. Find the first value n such that P(n) is at least a given target number.

Advent of Code: Day 19

2015-12-19

Source

Part 1: Given a list of list of string replacements and an input string, determine how many unique output strings are possible after one step.

Advent of Code: Day 18

2015-12-18

Source

Part 1: Simulate Conway's Game of Life. Count how many lights are on after 100 iterations.

Advent of Code: Day 17

2015-12-17

Source

Part 1: Given a list of containers of varying sizes and a total volume to contain, determine how many different combinations of containers match exactly the given volume.

Advent of Code: Day 16

2015-12-16

Source

Part 1: Given a list of target values of the form:

children: 3
cats: 7
samoyeds: 2

And a list of ‘Aunt Sues’, each with known values:

Sue 1: children: 1, cars: 8, vizslas: 7
Sue 2: akitas: 10, perfumes: 10, children: 5
Sue 3: cars: 5, pomeranians: 4, vizslas: 1

Determine which Sue has no unset but matching values.

For example, Sue 1 is invalid because children is 1 versus 3 and Sue 2 because children is 5 versus 3. Given only the values above, Sue 3 would be valid since there are no contradictions.