#include "transfer.h"
#include <vector>
#include <iostream>
#include <cassert>
std::vector<int> get_attachment(std::vector<int> source) {
std::vector<int> res;
for (int i = 0; (1 << i) < source.size(); ++i) {
int xorsum = 0;
for (int j = 0; j < source.size(); ++j) {
if (((j >> i) & 1) == 0) continue;
xorsum ^= source[j];
}
res.push_back(xorsum);
}
int parity = 0;
for (int i : res) parity ^= i;
res.push_back(parity);
return res;
}
int log2(int n) {
int log = 0;
while (n) ++log, n >>= 1;
return log;
}
std::vector<int> retrieve(std::vector<int> data) {
int parity = data.back(); data.pop_back();
int extra = log2(data.size());
while (log2(data.size() - extra) < extra) --extra;
// std::cout << extra << std::endl;
// for (auto el : data) std::cout << el;
// std::cout << std::endl;
int bad = 0;
for (int i = 0; i < extra; ++i) {
int xorsum = data[data.size() - extra + i];
// std::cout << "INFO: " << xorsum << std::endl;
for (int j = 0; j < data.size() - extra; ++j) {
if (((j >> i) & 1) == 0) continue;
xorsum ^= data[j];
// std::cout << "INFOOO: " << xorsum << std::endl;
}
assert(xorsum <= 1);
bad ^= xorsum << i;
}
for (int i = data.size() - extra; i < data.size(); ++i) {
parity ^= data[i];
}
if (parity) bad = -1;
for (int i = 0; i < data.size(); ++i) {
data[i] ^= i==bad;
}
// std::cout << bad << std::endl;
std::vector<int> res;
for (int i = 0; i < data.size() - extra; ++i) {
res.push_back(data[i]);
}
return res;
}
