#include "message.h"
#include <bits/stdc++.h>
using namespace std;
using vb = vector<bool>;
using vvb = vector<vb>;
const vb ZERO(31, false);
const vb ONE(31, true);
void trace_vb(vb inp) {
for (int i = 0; i < (int) inp.size(); i++) {
cout << (inp[i] ? "1 " : "0 ");
}
cout << "\n";
}
void send_message(vb M, vb C) {
// Stage 1: broadcast the location of the first bit (4 packets)
int first = 0; while (C[first]) first++;
for (int i = 0; i < 4; i++) {
if (first & (1 << i)) send_packet(ONE);
else send_packet(ZERO);
}
// Stage 2: broadcast the information
vector<int> mask; for (int i = 0; i < 31; i++) if (!C[i]) mask.push_back(i);
int S = (int) M.size(), midx = 0;
for (int i = 0; i < 67; i++) {
vb packet(31, false);
if (i < 31) {
packet[first] = !C[i];
} else if (i < 42) {
int bit = i - 31;
packet[first] = S & (1 << bit);
}
if (midx < S) {
int start = i < 42 ? 1 : 0;
for (int off = start; off < 16 && midx < S; off++) {
packet[mask[off]] = M[midx++];
}
}
send_packet(packet);
}
}
vb receive_message(vvb R) {
vb M;
// Stage 1: Receive index of first bit
int first = 0;
for (int i = 0; i < 4; i++) {
int ones = 0; for (int bit = 0; bit < 31; bit++) ones += R[i][bit];
if (ones < 16) continue;
first |= (1 << i);
}
// Stage 2: Determine which bits are safe
vector<int> safe;
for (int i = 0; i < 31; i++) {
if (R[i + 4][first]) safe.push_back(i);
}
// Stage 3: Determine the length of the message
int length = 0;
for (int i = 0; i < 11; i++) {
if (R[i + 35][first]) length |= (1 << i);
}
// Stage 4: Determine message contents
for (int i = 0; i < 67; i++) {
int start = i < 42 ? 1 : 0;
for (int bit = start; bit < 16 && (int) M.size() < length; bit++) {
M.push_back(R[4 + i][safe[bit]]);
}
}
return M;
}
