Submission #839849

#TimeUsernameProblemLanguageResultExecution timeMemory
839849jtnydv25Longest Trip (IOI23_longesttrip)C++17
25 / 100
40 ms456 KiB
#include "longesttrip.h" #include <bits/stdc++.h> using namespace std; #define ll long long #define all(c) ((c).begin()), ((c).end()) #define sz(x) ((int)(x).size()) #ifdef LOCAL #include <print.h> #else #define trace(...) #define endl "\n" // remove in interactive #endif vector<vector<int>> remove(vector<vector<int>> P, int a, int b){ vector<vector<int>> ret; for(int i = 0; i < sz(P); i++) if(i != a && i != b) ret.push_back(P[i]); return ret; } vector<int> longest_trip(int n, int d){ vector<vector<int>> paths; vector<int> nodes(n), b(n - 1); iota(all(nodes), 0); random_shuffle(all(nodes)); // for(int i = 0; i < n - 1; i++){ // b[i] = are_connected({nodes[i]}, {nodes[i + 1]}); // } vector<int> vis(n); // for(int i = 0; i < n; i++) if(!vis[i]){ // int j = i; // vector<int> path; // while(j < n){ // path.push_back(nodes[j]); // vis[j] = true; // if(j == n - 1) break; // if(j < n - 1 && b[j]){ // j++; // continue; // } else if(j < n - 2 && !b[j + 1]){ // j += 2; // continue; // } // break; // } // paths.push_back(path); // } for(int i = 0; i < n; i++) paths.push_back({i}); if(sz(paths) == 1) return paths[0]; // return {}; while(sz(paths) > 2){ int k = sz(paths); int p = rand() % k, q = rand() % k, r = rand() % k; while(p == q || q == r || p == r){ p = rand() % k, q = rand() % k, r = rand() % k; } int pp = p, qq = q; if(!are_connected({paths[p][0]}, {paths[q][0]})){ if(rand() % 2) swap(p, q); if(are_connected({paths[q][0]}, {paths[r][0]})){ pp = q; qq = r; } else{ // qq = r; pp = p; qq = r; } } assert(are_connected({paths[pp][0]}, {paths[qq][0]})); vector<int> newpath = paths[pp]; reverse(all(newpath)); copy(all(paths[qq]), back_inserter(newpath)); paths = remove(paths, pp, qq); paths.push_back(newpath); } // for(int i = 0; i < 2; i++){ // for(int j = 0; j < 2; j++){ // if(are_connected({paths[0][0]}, {paths[1][0]})){ // vector<int> Q = paths[0]; // reverse(all(Q)); // copy(all(paths[1]), back_inserter(Q)); // return Q; // } // reverse(all(paths[1])); // } // reverse(all(paths[0])); // } // vector<int> P = paths[0], Q = paths[1]; // if(are_connected(paths[0], paths[1])){ // for(int i = 0; i < 2; i++){ // while(sz(paths[i]) > 1){ // int k = sz(paths[i]) / 2; // vector<int> lft(paths[i].begin(), paths[i].begin() + k); // vector<int> rgt(paths[i].begin() + k, paths[i].end()); // if(are_connected(lft, paths[i ^ 1])){ // paths[i] = lft; // } else paths[i] = rgt; // } // } // vector<int> final_path; // int posP = find(all(P), paths[0][0]) - P.begin(); // int posQ = find(all(P), paths[0][0]) - P.begin(); // posP = (posP + 1) % sz(P); // rotate(P.begin(), P.begin() + posP, P.end()); // rotate(Q.begin(), Q.begin() + posQ, Q.end()); // copy(all(Q), back_inserter(P)); // return P; // } return sz(paths[0]) > sz(paths[1]) ? paths[0] : paths[1]; }
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