#include "robot.h"
#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#define ll long long
#define endl "\n"
using namespace std;
int H, W; // maze dimensions (provided by grader)
int PHASE = 0; // 0 = BFS expansion, 1 = traceback
int L = 0; // current BFS layer
int C = 2; // marker color = L%4 + 2
void program_pulibot()
{
vector<int> V = { -2, -1, 0, 1, 2, 3, 4, 5 };
vector<int> S(5);
auto mv = [&](int c) -> char {
if (c == 2) return 'W';
if (c == 3) return 'S';
if (c == 4) return 'E';
return 'N';
};
for (int s0 : V)
for (int s1 : V)
for (int s2 : V)
for (int s3 : V)
for (int s4 : V)
{
S[0] = s0; S[1] = s1; S[2] = s2; S[3] = s3; S[4] = s4;
if (PHASE == 0)
{
// --- BFS expansion phase ---
// 1) if on an unvisited cell at current layer, mark its parent pointer
if (s0 == 0 && s1 == C)
{
bool moved = false;
for (int d = 0; d < 4; d++)
{
if (S[d+2] == 0) // neighbor unvisited
{
int code = C + (d%4);
set_instruction(S, code, mv(code));
moved = true;
break;
}
}
if (moved) continue;
}
// 2) detect first arrival at goal → switch to traceback
if (s0 == 0 && s2 == -2 && s3 == -2)
{
PHASE = 1;
set_instruction(S, 1, 'T');
continue;
}
// 3) after sweeping all of layer L, advance to next layer
// (we see no S[1]==C anymore)
bool any_at_layer = false;
for (int x : V)
if (x == C) { any_at_layer = true; break; }
if (!any_at_layer)
{
L++;
C = 2 + (L % 4);
}
// 4) on all other states, stay put
set_instruction(S, 0, 'H');
}
else
{
// --- traceback phase ---
if (s0 >= 2 && s0 <= 5)
{
set_instruction(S, 1, mv(s0));
}
else
{
set_instruction(S, 0, 'H');
}
}
}
}
