forked from Bananymous/banan-os
121 lines
2.1 KiB
C++
121 lines
2.1 KiB
C++
#include <BAN/HashMap.h>
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#include <BAN/StringView.h>
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#include <BAN/Vector.h>
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#include <inttypes.h>
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#include <stdio.h>
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using i8 = int8_t;
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using i16 = int16_t;
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using i32 = int32_t;
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using i64 = int64_t;
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using u8 = uint8_t;
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using u16 = uint16_t;
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using u32 = uint32_t;
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using u64 = uint64_t;
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u64 even_divisor(u64 stone)
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{
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u8 digits = 0;
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for (u64 mult = 1; mult <= stone; mult *= 10)
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digits++;
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if (digits % 2)
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return 0;
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u64 divisor = 1;
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for (u8 i = 0; i < digits / 2; i++)
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divisor *= 10;
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return divisor;
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}
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u64 count_stones(u64 stone, u8 depth)
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{
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static BAN::HashMap<u64, u64> cache;
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if (depth == 0)
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return 1;
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const u64 cache_key = (stone << 8) | depth;
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auto it = cache.find(cache_key);
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if (it != cache.end())
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return it->value;
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if (stone == 0)
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return count_stones(1, depth - 1);
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u64 divisor = even_divisor(stone);
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if (divisor == 0)
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return count_stones(stone * 2024, depth - 1);
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u64 result = 0;
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result += count_stones(stone / divisor, depth - 1);
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result += count_stones(stone % divisor, depth - 1);
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MUST(cache.insert(cache_key, result));
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return result;
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}
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i64 part1(FILE* fp)
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{
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BAN::Vector<u64> stones;
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char buffer[128];
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ASSERT (fgets(buffer, sizeof(buffer), fp));
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{
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auto strs = MUST(BAN::StringView(buffer).split(' '));
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for (auto str : strs)
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MUST(stones.push_back(atoll(str.data())));
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}
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u64 result = 0;
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for (size_t i = 0; i < stones.size(); i++)
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result += count_stones(stones[i], 25);
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return result;
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}
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i64 part2(FILE* fp)
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{
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BAN::Vector<u64> stones;
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char buffer[128];
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ASSERT (fgets(buffer, sizeof(buffer), fp));
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{
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auto strs = MUST(BAN::StringView(buffer).split(' '));
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for (auto str : strs)
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MUST(stones.push_back(atoll(str.data())));
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}
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u64 result = 0;
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for (size_t i = 0; i < stones.size(); i++)
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result += count_stones(stones[i], 75);
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return result;
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}
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int main(int argc, char** argv)
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{
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const char* file_path = "/usr/share/aoc2024/day11_input.txt";
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if (argc >= 2)
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file_path = argv[1];
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FILE* fp = fopen(file_path, "r");
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if (fp == nullptr)
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{
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perror("fopen");
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return 1;
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}
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printf("part1: %" PRId64 "\n", part1(fp));
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fseek(fp, 0, SEEK_SET);
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printf("part2: %" PRId64 "\n", part2(fp));
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fclose(fp);
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}
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