AoC-2024

Advent of Code 2024 Day 1: Day 2: Day 3: Day 4: Day 5: Day 6: Guard Patroling Part 1: simple while loop until out-of-bound position detected. Refactoring turning logic helps code clean Part 2: keeps track every obstacle on which side it has been hit. If the same side was hit twice, the loop is detected. Day 7: Operator Serach Part 1: Recursion for O(2^n) with optimization via early termination, which was possible because + and * only increase the value Part 2: From O(2^n) to O(3^n). The same optimization is applied as concatenation has the same nature as + and * Day 8: Antenna Harmonic Part 1: Use the vector notation to find the antinode location. Leaving the out-of-grid check until we are going to add the location to final output. The final output handles duplication naturally through built-in set Part 2: Code changes by having the out-of-grid check embedded inside the antinode finding function. The while loop keeps adding the antinode as long as it is still inside grid. Day 9: File array compaction Part 1: Use two pointers to swap the empty space with file block. Part 2: Quite lots more complex than part 1. Settled with LinkedList approach in which every link node store the free space information: space left and the files that end up moving to this node (for later full expansion to get checksum). Every file moves from right-most tto left-most-that-fits cost O(n free node) so the overall is O(n2).