#include "transfer.h"
#include <bits/stdc++.h>
using namespace std;
std::vector<int> get_attachment(std::vector<int> source) {
int xor_zeroes = 0;
int N = (int)source.size();
for(int i = 0; i < N; ++i) if(source[i] == 0) xor_zeroes ^= i+1; //0-based can be misinfomation
vector<int> attachment;
int parity = 0;
for(int i = 0; (1 << i) <= N; ++i) {
attachment.push_back((xor_zeroes >> i & 1));
if(xor_zeroes >> i & 1) parity ^= 1;
}
attachment.push_back(parity);
return attachment;
}
std::vector<int> retrieve(std::vector<int> data) {
int L = (int)data.size();
int N = -1, bits = -1;
// for(int i = 0; i < L; ++i) cout << data[i]; cout << '\n';
for(int i = 1; i < L; ++i){
int b = 0;
while((1 << b) <= i) ++b;
if(i + b + 1 == L){
N = i;
bits = b;
break;
}
}
// cout << N << ' ' << bits << '\n';
assert(N != -1);
vector<int> attachment;
for(int i = 0; i < bits; ++i) attachment.push_back(data[N + i]);
int A = 0, B = 0, parity1 = data.back(), parity2 = 0;
for(int i = 0; i < N; ++i) if(data[i] == 0) A ^= i+1;
for(int i = 0; i < bits; ++i) if(attachment[i]) B ^= (1 << i), parity2 ^= 1;
// cout << parity1 << ' ' << parity2 << '\n';
if(parity1 != parity2){
return vector<int>(data.begin(), data.begin() + N);
}
int incorrect = A ^ B;
// cout << A << ' ' << B << '\n';
if(!incorrect) return vector<int>(data.begin(), data.begin() + N);
// cout << incorrect << '\n';
data[incorrect-1] ^= 1;
return vector<int>(data.begin(), data.begin() + N);
}
