Submission #840520

#	Time	Username	Problem	Language	Result	Execution time	Memory
840520		arbuzick	Longest Trip (IOI23_longesttrip)	C++17	40 / 100	892 ms	512 KiB

longesttrip

#include <bits/stdc++.h>

#include "longesttrip.h"

using namespace std;

vector<int> longest_trip(int n, int d) {
    if (d == 3) {
        vector<int> ans(n);
        iota(ans.begin(), ans.end(), 0);
        return ans;
    }
    if (d == 2) {
        vector<int> ans = {0};
        vector<int> used(n);
        used[0] = 1;
        while (ans.size() < n) {
            int nxt = -1;
            for (int i = 0; i < n; ++i) {
                if (!used[i] && are_connected({ans.back()}, {i})) {
                    nxt = i;
                    used[i] = 1;
                    break;
                }
            }
            if (nxt == -1) {
                reverse(ans.begin(), ans.end());
                for (int i = 0; i < n; ++i) {
                    if (!used[i] && are_connected({ans.back()}, {i})) {
                        nxt = i;
                        used[i] = 1;
                        break;
                    }
                }
            }
            ans.push_back(nxt);
        }
        return ans;
    }
    if (d == 1) {
        vector<vector<int>> g(n, vector<int>(n));
        for (int i = 0; i < n; ++i) {
            for (int j = i + 1; j < n; ++j) {
                if (are_connected({i}, {j})) {
                    g[i][j] = g[j][i] = 1;
                }
            }
        }
        vector<int> ans = {0};
        vector<int> used(n);
        used[0] = 1;
        auto try_to_add = [&]() {
            int nxt = -1;
            for (int i = 0; i < n; ++i) {
                if (!used[i] && g[ans.back()][i]) {
                    nxt = i;
                    used[i] = 1;
                    break;
                }
            }
            if (nxt == -1) {
                return false;
            }
            ans.push_back(nxt);
            return true;
        };
        while (true) {
            if (!try_to_add()) {
                break;
            }
        }
        // if (ans.size() < n) {
        //     reverse(ans.begin(), ans.end());
        //     if (try_to_add()) {
        //         while (true) {
        //             if (!try_to_add()) {
        //                 break;
        //             }
        //         }
        //     } else {
        //         for (int _ = 0; _ < (int)ans.size(); ++_) {
        //             reverse(ans.begin(), ans.end());
        //             int vl = ans.back();
        //             ans.pop_back();
        //             reverse(ans.begin(), ans.end());
        //             ans.push_back(vl);
        //             if (try_to_add()) {
        //                 while (true) {
        //                     if (!try_to_add()) {
        //                         break;
        //                     }
        //                 }
        //                 break;
        //             }
        //         }
        //     }
        // }
        if (ans.size() * 2 < n) {
            ans.clear();
            for (int i = 0; i < n; ++i) {
                if (!used[i]) {
                    ans.push_back(i);
                }
            }
        }
        return ans;
    }
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:17:27: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   17 |         while (ans.size() < n) {
      |                ~~~~~~~~~~~^~~
longesttrip.cpp:98:28: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   98 |         if (ans.size() * 2 < n) {
      |             ~~~~~~~~~~~~~~~^~~
longesttrip.cpp:108:1: warning: control reaches end of non-void function [-Wreturn-type]
  108 | }
      | ^

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 0 / 60