--- Day 11: Dumbo Octopus --- You enter a large cavern full of rare bioluminescent dumbo octopuses! They seem to not like the Christmas lights on your submarine, so you turn them off for now. There are 100 octopuses arranged neatly in a 10 by 10 grid. Each octopus slowly gains energy over time and flashes brightly for a moment when its energy is full. Although your lights are off, maybe you could navigate through the cave without disturbing the octopuses if you could predict when the flashes of light will happen. Each octopus has an energy level - your submarine can remotely measure the energy level of each octopus (your puzzle input). For example: 5483143223 2745854711 5264556173 6141336146 6357385478 4167524645 2176841721 6882881134 4846848554 5283751526 The energy level of each octopus is a value between 0 and 9. Here, the top-left octopus has an energy level of 5, the bottom-right one has an energy level of 6, and so on. You can model the energy levels and flashes of light in steps. During a single step, the following occurs: First, the energy level of each octopus increases by 1. Then, any octopus with an energy level greater than 9 flashes. This increases the energy level of all adjacent octopuses by 1, including octopuses that are diagonally adjacent. If this causes an octopus to have an energy level greater than 9, it also flashes. This process continues as long as new octopuses keep having their energy level increased beyond 9. (An octopus can only flash at most once per step.) Finally, any octopus that flashed during this step has its energy level set to 0, as it used all of its energy to flash. Adjacent flashes can cause an octopus to flash on a step even if it begins that step with very little energy. Consider the middle octopus with 1 energy in this situation: Before any steps: 11111 19991 19191 19991 11111 After step 1: 34543 40004 50005 40004 34543 After step 2: 45654 51115 61116 51115 45654 An octopus is highlighted when it flashed during the given step. Here is how the larger example above progresses: Before any steps: 5483143223 2745854711 5264556173 6141336146 6357385478 4167524645 2176841721 6882881134 4846848554 5283751526 After step 1: 6594254334 3856965822 6375667284 7252447257 7468496589 5278635756 3287952832 7993992245 5957959665 6394862637 After step 2: 8807476555 5089087054 8597889608 8485769600 8700908800 6600088989 6800005943 0000007456 9000000876 8700006848 After step 3: 0050900866 8500800575 9900000039 9700000041 9935080063 7712300000 7911250009 2211130000 0421125000 0021119000 After step 4: 2263031977 0923031697 0032221150 0041111163 0076191174 0053411122 0042361120 5532241122 1532247211 1132230211 After step 5: 4484144000 2044144000 2253333493 1152333274 1187303285 1164633233 1153472231 6643352233 2643358322 2243341322 After step 6: 5595255111 3155255222 3364444605 2263444496 2298414396 2275744344 2264583342 7754463344 3754469433 3354452433 After step 7: 6707366222 4377366333 4475555827 3496655709 3500625609 3509955566 3486694453 8865585555 4865580644 4465574644 After step 8: 7818477333 5488477444 5697666949 4608766830 4734946730 4740097688 6900007564 0000009666 8000004755 6800007755 After step 9: 9060000644 7800000976 6900000080 5840000082 5858000093 6962400000 8021250009 2221130009 9111128097 7911119976 After step 10: 0481112976 0031112009 0041112504 0081111406 0099111306 0093511233 0442361130 5532252350 0532250600 0032240000 After step 10, there have been a total of 204 flashes. Fast forwarding, here is the same configuration every 10 steps: After step 20: 3936556452 5686556806 4496555690 4448655580 4456865570 5680086577 7000009896 0000000344 6000000364 4600009543 After step 30: 0643334118 4253334611 3374333458 2225333337 2229333338 2276733333 2754574565 5544458511 9444447111 7944446119 After step 40: 6211111981 0421111119 0042111115 0003111115 0003111116 0065611111 0532351111 3322234597 2222222976 2222222762 After step 50: 9655556447 4865556805 4486555690 4458655580 4574865570 5700086566 6000009887 8000000533 6800000633 5680000538 After step 60: 2533334200 2743334640 2264333458 2225333337 2225333338 2287833333 3854573455 1854458611 1175447111 1115446111 After step 70: 8211111164 0421111166 0042111114 0004211115 0000211116 0065611111 0532351111 7322235117 5722223475 4572222754 After step 80: 1755555697 5965555609 4486555680 4458655580 4570865570 5700086566 7000008666 0000000990 0000000800 0000000000 After step 90: 7433333522 2643333522 2264333458 2226433337 2222433338 2287833333 2854573333 4854458333 3387779333 3333333333 After step 100: 0397666866 0749766918 0053976933 0004297822 0004229892 0053222877 0532222966 9322228966 7922286866 6789998766 After 100 steps, there have been a total of 1656 flashes. Given the starting energy levels of the dumbo octopuses in your cavern, simulate 100 steps. How many total flashes are there after 100 steps? Your puzzle answer was 1675. --- Part Two --- It seems like the individual flashes aren't bright enough to navigate. However, you might have a better option: the flashes seem to be synchronizing! In the example above, the first time all octopuses flash simultaneously is step 195: After step 193: 5877777777 8877777777 7777777777 7777777777 7777777777 7777777777 7777777777 7777777777 7777777777 7777777777 After step 194: 6988888888 9988888888 8888888888 8888888888 8888888888 8888888888 8888888888 8888888888 8888888888 8888888888 After step 195: 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 If you can calculate the exact moments when the octopuses will all flash simultaneously, you should be able to navigate through the cavern. What is the first step during which all octopuses flash? Your puzzle answer was 515. 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. If you still want to see it, you can get your puzzle input. You can also [Share] this puzzle.