Submission #563935

#	Time	Username	Problem	Language	Result	Execution time	Memory
563935		tengiz05	전압 (JOI14_voltage)	C++17	100 / 100	518 ms	42052 KiB

voltage

#include <bits/stdc++.h>

using i64 = long long;

void solve() {
    int n, m;
    std::cin >> n >> m;
    
    std::vector<std::vector<int>> e(n);
    
    std::map<std::pair<int, int>, int> id, cnt;
    
    for (int i = 0; i < m; i++) {
        int u, v;
        std::cin >> u >> v;
        u--;
        v--;
        e[u].push_back(v);
        e[v].push_back(u);
        id[std::minmax(u, v)] = i;
        cnt[std::minmax(u, v)]++;
    }
    
    std::vector<int> color(n, -1), p(n), dep(n);
    p[0] = -1;
    std::function<void(int)> dfs = [&](int u) {
        for (int v : e[u]) {
            if (color[v] == -1) {
                p[v] = u;
                dep[v] = dep[u] + 1;
                color[v] = color[u] ^ 1;
                dfs(v);
            }
        }
    };
    for (int i = 0; i < n; i++) {
        if (color[i] == -1) {
            color[i] = 0;
            p[i] = -1;
            dfs(i);
        }
    }
    
    std::vector<int> f(n);
    
    int badEdges = 0;
    for (int u = 0; u < n; u++) {
        for (int v : e[u]) {
            if (dep[u] < dep[v] && p[v] != u) {
                if (color[u] == color[v]) {
                    badEdges++;
                    f[v]++;
                    f[u]--;
                } else {
                    f[v]--;
                    f[u]++;
                }
            }
        }
    }
    
    std::vector<bool> vis(n);
    dfs = [&](int u) {
        vis[u] = true;
        for (int v : e[u]) {
            if (p[v] == u && !vis[v]) {
                dfs(v);
                f[u] += f[v];
            }
        }
    };
    for (int i = 0; i < n; i++) {
        if (!vis[i]) {
            dfs(i);
        }
    }
    
    std::vector<int> ans;
    
    if (badEdges == 1) {
        for (auto [p, i] : id) {
            if (color[p.first] == color[p.second] && cnt[std::minmax(p.first, p.second)] == 1) {
                ans.push_back(i);
            }
        }
    }
    
    for (int i = 1; i < n; i++) {
        if (f[i] == badEdges && cnt[std::minmax(p[i], i)] == 1) {
            ans.push_back(id[std::minmax(p[i], i)]);
        }
    }
    
    std::sort(ans.begin(), ans.end());
    std::cout << ans.size() << "\n";
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int t = 1;
    // std::cin >> t;
    
    while (t--) {
        solve();
    }
    
    return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 35 / 35
• Subtask 4: 45 / 45