126 lines
2.2 KiB
C++
126 lines
2.2 KiB
C++
#include <BAN/String.h>
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#include <BAN/Vector.h>
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#include <ctype.h>
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#include <inttypes.h>
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#include <stdio.h>
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#include <stdint.h>
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using i32 = int32_t;
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using i64 = int64_t;
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using u32 = uint32_t;
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using u64 = uint64_t;
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i64 parse_i64(BAN::StringView sv)
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{
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bool negative = (!sv.empty() && sv.front() == '-');
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if (negative)
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sv = sv.substring(1);
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i64 result = 0;
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for (char c : sv)
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{
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if (!isdigit(c))
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break;
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result = (result * 10) + (c - '0');
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}
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return negative ? -result : result;
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}
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BAN::Vector<BAN::Vector<i64>> build_difference_tree(BAN::StringView input)
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{
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auto value_strs = MUST(input.split(' '));
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if (value_strs.empty())
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return {};
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BAN::Vector<BAN::Vector<i64>> tree;
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MUST(tree.emplace_back(value_strs.size(), 0));
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for (size_t i = 0; i < value_strs.size(); i++)
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tree.back()[i] = parse_i64(value_strs[i]);
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bool all_zeroes = false;
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while (!all_zeroes)
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{
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size_t last = tree.size();
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MUST(tree.emplace_back(tree.back().size() - 1, 0));
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all_zeroes = true;
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for (size_t i = 0; i < tree.back().size(); i++)
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{
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i64 lhs = tree[last - 1][i + 0];
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i64 rhs = tree[last - 1][i + 1];
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tree[last][i] = rhs - lhs;
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if (tree[last][i] != 0)
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all_zeroes = false;
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}
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}
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return tree;
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}
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i64 puzzle1(FILE* fp)
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{
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i64 result = 0;
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char buffer[128];
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while (fgets(buffer, sizeof(buffer), fp))
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{
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auto tree = build_difference_tree(buffer);
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if (tree.empty())
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continue;
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i64 current = 0;
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for (size_t i = tree.size(); i > 0; i--)
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current = tree[i - 1].back() + current;
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result += current;
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}
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return result;
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}
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i64 puzzle2(FILE* fp)
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{
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i64 result = 0;
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char buffer[128];
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while (fgets(buffer, sizeof(buffer), fp))
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{
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auto tree = build_difference_tree(buffer);
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if (tree.empty())
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continue;
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i64 current = 0;
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for (size_t i = tree.size(); i > 0; i--)
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current = tree[i - 1].front() - current;
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result += current;
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}
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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/aoc2023/day9_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("puzzle1: %" PRId64 "\n", puzzle1(fp));
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fseek(fp, 0, SEEK_SET);
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printf("puzzle2: %" PRId64 "\n", puzzle2(fp));
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fclose(fp);
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}
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