#include <BAN/String.h> #include <BAN/Vector.h> #include <ctype.h> #include <inttypes.h> #include <stdio.h> #include <stdint.h> using i32 = int32_t; using i64 = int64_t; using u32 = uint32_t; using u64 = uint64_t; i64 parse_i64(BAN::StringView sv) { bool negative = (!sv.empty() && sv.front() == '-'); if (negative) sv = sv.substring(1); i64 result = 0; for (char c : sv) { if (!isdigit(c)) break; result = (result * 10) + (c - '0'); } return negative ? -result : result; } BAN::Vector<BAN::Vector<i64>> build_difference_tree(BAN::StringView input) { auto value_strs = MUST(input.split(' ')); if (value_strs.empty()) return {}; BAN::Vector<BAN::Vector<i64>> tree; MUST(tree.emplace_back(value_strs.size(), 0)); for (size_t i = 0; i < value_strs.size(); i++) tree.back()[i] = parse_i64(value_strs[i]); bool all_zeroes = false; while (!all_zeroes) { size_t last = tree.size(); MUST(tree.emplace_back(tree.back().size() - 1, 0)); all_zeroes = true; for (size_t i = 0; i < tree.back().size(); i++) { i64 lhs = tree[last - 1][i + 0]; i64 rhs = tree[last - 1][i + 1]; tree[last][i] = rhs - lhs; if (tree[last][i] != 0) all_zeroes = false; } } return tree; } i64 puzzle1(FILE* fp) { i64 result = 0; char buffer[128]; while (fgets(buffer, sizeof(buffer), fp)) { auto tree = build_difference_tree(buffer); if (tree.empty()) continue; i64 current = 0; for (size_t i = tree.size(); i > 0; i--) current = tree[i - 1].back() + current; result += current; } return result; } i64 puzzle2(FILE* fp) { i64 result = 0; char buffer[128]; while (fgets(buffer, sizeof(buffer), fp)) { auto tree = build_difference_tree(buffer); if (tree.empty()) continue; i64 current = 0; for (size_t i = tree.size(); i > 0; i--) current = tree[i - 1].front() - current; result += current; } return result; } int main(int argc, char** argv) { const char* file_path = "/usr/share/aoc2023/day9_input.txt"; if (argc >= 2) file_path = argv[1]; FILE* fp = fopen(file_path, "r"); if (fp == nullptr) { perror("fopen"); return 1; } printf("puzzle1: %" PRId64 "\n", puzzle1(fp)); fseek(fp, 0, SEEK_SET); printf("puzzle2: %" PRId64 "\n", puzzle2(fp)); fclose(fp); }