Submission #1074000

#	Time	Username	Problem	Language	Result	Execution time	Memory
1074000		deera	Friend (IOI14_friend)	C++14	19 / 100	410 ms	65536 KiB

friend

#include <bits/stdc++.h>
using namespace std;

const int MAXN = 1e5+5;
set<int> adj[MAXN];

// Find out best sample
int findSample(int n, int confidence[], int host[], int protocol[]){
    for (int i = 0; i < n; i++) {
        if (i == 0) continue;
        int h = host[i];
        switch (protocol[i]) {
            case 0:
                // I am your friend
                adj[h].insert(i);
                adj[i].insert(h);
                break;
            case 1:
                // my friends are your friends
                for (int f: adj[h]) {
                    if (h == f) continue;
                    adj[i].insert(f);
                    adj[f].insert(i);
                }
                break;

            case 2:
                // we are your friends
                adj[h].insert(i);
                adj[i].insert(h);

                for (int f: adj[h]) {
                    if (h == f) continue;
                    adj[i].insert(f);
                    adj[f].insert(i);
                }
                break;
        }
    }

    // a friend can't be a friend of themselves
    for (int i = 0; i < n; i++) adj[i].erase(i);

    // for (int i = 0; i < n; i++) {
    //     cerr << i << ": ";
    //     for (auto x: adj[i]) cerr << x << " ";
    //     cerr << endl;
    // }

    if (n <= 10) {
        int max_ans = 0;
        int ans = 0;
        for (int i = 0; i < (1 << n); i++) {
            set<int> s;
            for (int j = 0; j < n; j++)
                if (i & (1 << j)) s.insert(j);

            bool ok = true;
            for (auto x: s)
                for (auto f: adj[x])
                    if (s.count(f)) {
                        ok = false;
                        break;
                    }

            if (!ok) continue;
            for (auto x: s) ans += confidence[x];
            max_ans = max(max_ans, ans);
            ans = 0;
        }

        return max_ans;
    }

    int hist[3] = {0, 0, 0};
    for (int i = 0; i < n; i++) hist[protocol[i]]++;

    if (hist[1] == n) {
        int ans = 0;
        for (int i = 0; i < n; i++) ans += confidence[i];
        return ans;
    }
}

Compilation message (stderr)

friend.cpp: In function 'int findSample(int, int*, int*, int*)':
friend.cpp:83:1: warning: control reaches end of non-void function [-Wreturn-type]
   83 | }
      | ^

• Subtask 1: 11 / 11
• Subtask 2: 8 / 8
• Subtask 3: 0 / 8
• Subtask 4: 0 / 19
• Subtask 5: 0 / 23
• Subtask 6: 0 / 31