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#include "aoc.h"
#include <map>
namespace aoc2022 {
static int64_t pow(size_t n) {
int64_t x{1};
for (size_t i = 0; i < n; i++) {
x *= 5;
}
return x;
}
int64_t pow5(size_t n) {
static std::vector<int64_t> ns;
if (n >= ns.size()) {
auto s = ns.size();
ns.resize(n + 1);
for (size_t i = s; i < ns.size(); i++) {
ns[i] = pow(i);
}
}
return ns[n];
}
int64_t base10(snafu s) {
int64_t x{0};
for (size_t i = 0; i < s.length; i++) {
switch (*(s.digits + i)) {
case '=':
x = x * 5 - 2;
break;
case '-':
x = x * 5 - 1;
break;
case '0':
x = x * 5;
break;
case '1':
x = x * 5 + 1;
break;
case '2':
x = x * 5 + 2;
break;
default:
break;
}
}
return x;
}
struct snafu_digit {
int64_t l;
int64_t m1;
int64_t d1;
int64_t d2;
int64_t m2;
int64_t h;
};
snafu_digit range(size_t n) {
static std::map<size_t, snafu_digit> cache;
auto p = cache.insert({n, {}});
if (p.second) {
int64_t m1 = pow5(n);
int64_t m2 = 2 * m1;
int64_t d1 = (m1 + m2) / 2;
int64_t d2 = d1 + 1;
int64_t l = m1;
for (size_t i = n; i > 0; i--) {
l -= 2 * pow5(i - 1);
}
int64_t h = m2;
for (size_t i = n; i > 0; i--) {
h += 2 * pow5(i - 1);
}
p.first->second = {l, m1, d1, d2, m2, h};
}
return p.first->second;
}
void decode(int64_t x, size_t n, std::vector<int>& is) {
if (n == 0) {
is.push_back(x);
} else {
int64_t sign = x == 0 ? 0 : x > 0 ? 1 : -1;
auto r = range(n);
auto ax = std::abs(x);
if (ax < r.l) {
is.push_back(0);
decode(x, n - 1, is);
}
if (ax >= r.l && ax < r.d2) {
is.push_back(sign * 1);
decode(x - sign * r.m1, n - 1, is);
}
if (ax >= r.d2) {
is.push_back(sign * 2);
decode(x - sign * r.m2, n - 1, is);
}
}
}
std::string baseSNAFU(int64_t x) {
size_t n{0};
while (true) {
auto p = range(n);
if (x >= p.l && x <= p.h) {
break;
}
n++;
}
std::vector<int> is;
decode(x, n, is);
std::string s;
char encodings[] = {'0', '1', '2', '=', '-'};
for (auto& i : is) {
s.push_back(i >= 0 ? encodings[i] : encodings[i + 5]);
}
return s;
}
std::pair<std::string, int64_t> day25(line_view file) {
std::vector<snafu> ss;
per_line(file, [&ss](line_view lv) {
ss.emplace_back(lv);
return true;
});
int64_t x{0};
for (auto& s : ss) {
// s.print();
// printf(" %ld\n", base10(s));
x += base10(s);
}
// printf("%ld %s\n", x, baseSNAFU(x).c_str());
return {baseSNAFU(x), 0};
}
} // namespace aoc2022
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