#include "transfer.h"
#include <bits/stdc++.h>
using namespace std;
int calcXor(vector<int> &a, int l, int r) {
int x = 0;
for (int i=l; i<=r; i++) x ^= a[i];
return x;
}
vector<int> calculateXors(vector<int> &source) {
int n = 1;
while (n < (int)source.size()) n <<= 1;
vector<int> tmp(n, 0);
for (int i=0; i<(int)source.size(); i++) tmp[i] = source[i];
vector<int> bits;
for (int b=0; (1 << b) < n; b++) {
int Xor = 0;
for (int i=0; i<n; i+=2*(1 << b)) {
Xor ^= calcXor(tmp, i, i+(1 << b)-1);
}
bits.push_back(Xor);
}
reverse(bits.begin(), bits.end());
bits.push_back(calcXor(source, 0, (int)source.size() - 1));
return bits;
}
vector<int> get_attachment(vector<int> source) {
return calculateXors(source);
}
vector<int> retrieve(vector<int> data) {
// for (int d : data) cout << d << ' ';
// cout << endl;
int n;
if ((int)data.size() <= 100) n = 63;
else n = 255;
vector<int> src(n);
for (int i=0; i<n; i++) src[i] = data[i];
vector<int> bits;
for (int i=n; i<(int)data.size()-1; i++)
bits.push_back(data[i]);
int checkerBit = data.back();
vector<int> expectedBits = calculateXors(src);
int expectedChecker = expectedBits.back();
if (expectedChecker == checkerBit) {
return src;
} // corrompeu bits
int l = 0, r = n-1; int pt = 0, ans = -1;
while (l <= r) {
int m = (l + r) / 2;
if (bits[pt] != expectedBits[pt]) {
r = m-1;
ans = m;
} else l = m+1;
pt++;
}
if (ans != -1) src[ans] = !src[ans];
return src;
}
