#include "islands.h" #include <bits/stdc++.h> using namespace std; using idata = vector<int>; using igrid = vector<idata>; using bdata = vector<bool>; igrid roads; bdata visited; bdata visiting; idata path; bool dfs (int node) { if (visiting[node]) { path.push_back(node); return true; } if (visited[node]) return false; path.push_back(node); visited[node] = true; visiting[node] = true; for (int next : roads[node]) if (dfs(next)) return true; visiting[node] = false; path.pop_back(); return false; } std::variant<bool, idata> find_journey( int N, int M, idata U, idata V) { roads.resize(N); visited.resize(N); visiting.resize(N); bool st3 = M % 2 == 0; for (int i = 0; i < M; i ++) roads[U[i]].push_back(V[i]); for (int i = 0; i + 1 < M; i += 2) st3 &= (U[i] == U[i + 1]) && (V[i] == V[i + 1]); if (!dfs(0)) return false; idata dpath; idata cycle; int joint = path[path.size() - 1]; bool f_joint = false; for (int i = 0; i + 1 < path.size(); i ++) { if (f_joint) cycle.push_back(path[i]); else if (path[i] != joint) dpath.push_back(path[i]); f_joint |= path[i] == joint; } idata answer; if (st3) { // dpath + (joint + cycle) * 2 + (joint + cycle^-1) * 2 + joint + dpath^-1 for (int u : dpath) answer.push_back(u); answer.push_back(joint); for (int u : cycle) answer.push_back(u); answer.push_back(joint); for (int u : cycle) answer.push_back(u); reverse(cycle.begin(), cycle.end()); answer.push_back(joint); for (int u : cycle) answer.push_back(u); answer.push_back(joint); for (int u : cycle) answer.push_back(u); answer.push_back(joint); reverse(dpath.begin(), dpath.end()); for (int u : dpath) answer.push_back(u); } return answer; }

islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, idata, idata)':
islands.cpp:52:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   52 |   for (int i = 0; i + 1 < path.size(); i ++) {
      |                   ~~~~~~^~~~~~~~~~~~~