#include <iostream>
#include <vector>
#include <deque>
#include <set>
using namespace std;
void answer(int X);
void count_routes(int N, int M, int P, int R[][2], int Q, int G[]) {
// Build adjacency lists, but only keep up to 2 edges per node
vector<vector<int>> node_edges(N + 1);
for (int idx = 0; idx < M; ++idx) {
int i = R[idx][0];
int j = R[idx][1];
if (node_edges[i].size() < 2) {
node_edges[i].push_back(j);
}
if (node_edges[j].size() < 2) {
node_edges[j].push_back(i);
}
}
// Walk function: choose the neighbor that's not the one we came from
auto do_walk = [&](int walk, int prev_walk) {
if (node_edges[walk].empty()) {
// No neighbors, same
return walk;
}
int next_walk = node_edges[walk][0];
if (node_edges[walk].size() == 2 && next_walk == prev_walk) {
next_walk = node_edges[walk][1];
}
return next_walk;
};
// Can we, starting from `node`, after g steps end up at node P?
auto can_from_node = [&](int node, int g) {
deque<pair<int,int>> path;
set<pair<int,int>> visited;
int prev_walk = node;
int walk = do_walk(prev_walk, -1);
int next_walk = do_walk(walk, prev_walk); // uses default prev_walk = -1
while (g > 0) {
pair<int,int> state = make_pair(walk, next_walk);
if (visited.find(state) == visited.end()) {
visited.insert(state);
path.push_back(state);
g--;
int temp = walk;
walk = do_walk(walk, prev_walk);
if (temp == walk) {
return walk == P; // we are stuck at walk
}
prev_walk = temp;
next_walk = do_walk(walk, prev_walk);
} else {
g--;
std::cout << "hit cycle!" << std::endl;
std::cout << "g remaining " << g << std::endl;
std::cout << "path: " << std::endl;
for (int i = 0; i < path.size(); i++) {
std::cout << path[i].first << " " << path[i].second << std::endl;
}
std::cout << "state: " << state.first << " " << state.second << std::endl;
while (path.front() != state) {
std::cout << "popping " << path.front().first << " " << path.front().second << std::endl;
path.pop_front();
}
int c = path.size();
std::cout << "cycle length " << c << std::endl;
return path[g % c].first == P;
}
}
std::cout << "found path:" << '\n';
for (int i = 0; i < path.size(); i ++) {
std::cout << path[i].first << '\n';
}
std::cout << "--------" << '\n';
// After g steps, are we at P?
return path.back().first == P;
};
for (int i = 0; i < Q; i++) {
int g_val = G[i];
int count = 0;
std::cout << "i " << i << std::endl;
for (int node = 0; node < N; ++node) {
std::cout << "can from node: " << node << " " << g_val << std::endl;
bool can = can_from_node(node, g_val);
std::cout << "can from node " << node << " " << g_val << ": " << can << std::endl;
if (can) {
count++;
}
std::cout << "--------------------" << std::endl;
}
answer(count);
std::cout << "----------------------------------------" << std::endl;
}
}
