Submission #701989

#	Time	Username	Problem	Language	Result	Execution time	Memory
701989		Cyanmond	Friend (IOI14_friend)	C++17	30 / 100	24 ms	1504 KiB

friend

#include "friend.h"
#include <bits/stdc++.h>

int findSample(int n, int confidence[], int host[], int protocol[]) {
    if (n <= 10) {
        std::vector<std::vector<bool>> isFriend(n, std::vector<bool>(n));
        for (int x = 1; x < n; ++x) {
            const int h = host[x], type = protocol[x];
            if (type == 0) {
                isFriend[h][x] = isFriend[x][h] = true;
            } else if (type == 1) {
                for (int i = 0; i < n; ++i) {
                    if (isFriend[h][i]) {
                        isFriend[i][x] = isFriend[x][i] = true;
                    }
                }
            } else if (type == 2) {
                for (int i = 0; i < n; ++i) {
                    if (isFriend[h][i]) {
                        isFriend[i][x] = isFriend[x][i] = true;
                    }
                }
                isFriend[h][x] = isFriend[x][h] = true;
            }
        }

        int answer = 0;
        for (int bits = 0; bits < (1 << n); ++bits) {
            bool isOk = true;
            for (int i = 0; i < n; ++i) {
                if (not(bits & (1 << i))) {
                    continue;
                }
                for (int j = 0; j < n; ++j) {
                    if (not(bits & (1 << j))) {
                        continue;
                    }
                    if (isFriend[i][j]) {
                        isOk = false;
                    }
                }
            }
            int sum = 0;
            if (isOk) {
                for (int i = 0; i < n; ++i) {
                    if (not(bits & (1 << i))) {
                        continue;
                    }
                    sum += confidence[i];
                }
                answer = std::max(answer, sum);
            }
        }
        return answer;
    }

    bool ex0 = false, ex1 = false, ex2 = false;
    for (int i = 1; i < n; ++i) {
        if (protocol[i] == 0) {
            ex0 = true;
        }
        if (protocol[i] == 1) {
            ex1 = true;
        }
        if (protocol[i] == 2) {
            ex2 = true;
        }
    }
    if (ex0 and (not ex1) and (not ex2)) {
        // not prove
        std::vector<std::vector<bool>> isFriend(n, std::vector<bool>(n));
        for (int x = 1; x < n; ++x) {
            const int h = host[x], type = protocol[x];
            if (type == 0) {
                isFriend[h][x] = isFriend[x][h] = true;
            } else if (type == 1) {
                for (int i = 0; i < n; ++i) {
                    if (isFriend[h][i]) {
                        isFriend[i][x] = isFriend[x][i] = true;
                    }
                }
            }
        }
        std::vector<int> color(n, -1);
        int answer = 0;
        std::vector<std::pair<int, int>> dp(n, std::make_pair(0, 0));
        auto dfs = [&](auto &&self, const int v, const bool c) -> std::pair<int, int> {
            color[v] = c;
            auto &[a, b] = dp[v];
            for (int t = 0; t < n; ++t) {
                if ((not isFriend[v][t]) or color[t] != -1) {
                    continue;
                }
                auto [ra, rb] = self(self, t, not c);
                b += std::max(ra, rb);
                a += rb;
            }
            a += confidence[v];
            return {a, b};
        };
        dfs(dfs, 0, false);
        answer = std::max(dp[0].first, dp[0].second);
        return answer;
    }
    return -1;
}

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