Submission #1074040

#	Time	Username	Problem	Language	Result	Execution time	Memory
1074040		deera	Friend (IOI14_friend)	C++14	27 / 100	381 ms	65536 KiB

friend

#include <bits/stdc++.h>
using namespace std;
 
const int MAXN = 1e5+5;
set<int> adj[MAXN];
vector<int> CONF;

int dfs(int u, int p = -1, bool count = true) {
    int ans = 0;
    if (count) ans = CONF[u];
    for (auto v: adj[u]) {
        if (v == p) continue;
        ans += dfs(v, u, !count);
    }

    return ans;
}
 
// Find out best sample
int findSample(int n, int confidence[], int host[], int protocol[]){
    CONF.clear();
    for (int i = 0; i < n; i++) CONF.push_back(confidence[i]);

    int hist[3] = {0, 0, 0};
    int sum = 0;
    int maxi = 0;
    for (int i = 0; i < n; i++) {
        sum += confidence[i];
        maxi = max(maxi, confidence[i]);

        if (i == 0) continue;
        hist[protocol[i]]++;
    }

    if (hist[0] == 0 && hist[2] == 0) {
        return sum;
    }

    if (hist[0] == 0 && hist[1] == 0) {
        return maxi;
    }

    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]) {
                    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]) {
                    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 (hist[1] == 0 && hist[2] == 0) {
        int ans = dfs(0);
        return max(ans, abs(sum - ans));
    }
 
    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;
    }

    return 0;
}

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