Submission #980229

#	Time	Username	Problem	Language	Result	Execution time	Memory
980229		vjudge1	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	807 ms	2600 KiB

longesttrip

#include "longesttrip.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector <ll>;
using dll = deque <ll>;
using vi = vector <int>;

const ll MAXN = 256+16;
vll adj[MAXN];
bool mat[MAXN][MAXN];
ll comp[MAXN];

void dfs (ll u, ll col, ll &sz) {
    if (comp[u]) return;
    comp[u] = col;
    sz++;
    for (ll v : adj[u]) {
        dfs(v, col, sz);
    }
}

vi longest_trip (int n, int d) {
    fill(adj, adj+n+5, vll({}));
    fill(comp, comp+n+5, 0);
    for (ll u = 0; u < n; u++) {
        mat[u][u] = false;
        for (ll v = u+1; v < n; v++) {
            if (are_connected(vi({ int(u) }), vi({ int(v) }))) {
                adj[u].push_back(v);
                adj[v].push_back(u);
                mat[u][v] = true;
                mat[v][u] = true;
            } else {
                mat[u][v] = false;
                mat[v][u] = false;
            }
        }
    }
    ll c = 1;
    vll sz;
    for (ll u = 0; u < n; u++) {
        if (comp[u]) continue;
        sz.push_back(0);
        dfs(u, c++, sz.back());
    }
    assert(c == 2 || c == 3);
    if (c == 2) {
        vll fr, bk;
        fr.push_back(0);
        vector <char> vis(n, false);
        vis[0] = true;
        for (ll v = 0; v < n; v++) {
            if (mat[0][v]) {
                vis[v] = true;
                bk.push_back(v);
                break;
            }
        }
        assert(fr.size() == 1);
        assert(bk.size() == 1);
        ll skip = 0;
        for (ll u = 1; u < n; u++) {
            if (u == fr[0] || u == bk[0]) { skip++; continue; }
            if (mat[u][fr.back()]) {
                fr.push_back(u);
            } else if (mat[u][bk.back()]) {
                bk.push_back(u);
            } else assert(false);
        }
        // assert(skip == 0);
        vi ans(fr.rbegin(), fr.rend());
        for (ll i : bk) ans.push_back(i);
        return ans;
    } else if (c == 3) {
        assert(sz.size() == 2);
        if (sz[0] > sz[1]) {
            vi ans;
            for (ll u = 0; u < n; u++) {
                if (comp[u] == 1) {
                    ans.push_back(u);
                }
            }
            return ans;
        } else {
            vi ans;
            for (ll u = 0; u < n; u++) {
                if (comp[u] == 2) {
                    ans.push_back(u);
                }
            }
            return ans;
        }
    }
}

Compilation message (stderr)

longesttrip.cpp: In function 'vi longest_trip(int, int)':
longesttrip.cpp:41:9: warning: control reaches end of non-void function [-Wreturn-type]
   41 |     vll sz;
      |         ^~

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