#961439 (C++17) No.2286 Join Hands

• 問題: No.2286 Join Hands
• ユーザー: lgswdn
• 提出日時: 2024-03-17 10:27:41
• 言語: C++17 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 55 ms / 2,000 ms
• コード長: 2,105 bytes
• コンパイル時間: 2,126 ms
• コンパイル使用メモリ: 194,596 KB
• 最終ジャッジ日時: 2025-02-20 07:00:39
• ジャッジサーバーID （参考情報）: judge1 / judge2

ファイルパターン	結果
sample	AC * 3
other	AC * 58

ソースコード

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#include <bits/stdc++.h>
using namespace std;
const int N = 5e4 + 10;
int hd[10010], to[N], nx[N], W[N], tt = 1;
void add(int u, int v, int f) { to[++tt] = v, nx[tt] = hd[u], hd[u] = tt, W[tt] = f; }
void link(int u, int v, int f) { add(u, v, f), add(v, u, 0); }
int dep[N], cur[10010], q[N], l, r, S, T;
bool bfs() {
    q[l = r = 1] = S;
    memset(dep, 0, sizeof dep);
    dep[S] = 1;
    memcpy(cur, hd, sizeof cur);
    while (l <= r) {
        int u = q[l++];
        // cerr<<"POP: "<<u<<endl;
        for (int i = hd[u]; i; i = nx[i]) {
            int v = to[i];
            // cerr<<u<<"->"<<i<<" "<<W[i]<<" "<<v<<" "<<dep[v]<<endl;
            if (W[i] && !dep[v]) {
                dep[v] = dep[u] + 1;
                q[++r] = v;
            }
        }
    }
    return dep[T];
}
int dfs(int u, int f) {
    // cerr<<"DFS: "<<u<<" "<<f<<endl;
    if (u == T)
        return f;
    int r = 0, k;
    for (int& i = cur[u]; i; i = nx[i]) {
        int v = to[i];
        if (dep[v] == dep[u] + 1 && W[i]) {
            k = dfs(v, min(f, W[i]));
            r += k, f -= k;
            W[i] -= k, W[i ^ 1] += k;
        }
    }
    return r;
}
int Dinic() {
    int flow = 0;
    while (bfs()) /*cerr<<flow<<" : ",*/
        flow += dfs(S, 0x3f3f3f3f);
    return flow;
}
int ban[N];
int main() {
    cin.tie(0)->sync_with_stdio(0);
    int C, Tr=1;
    while (Tr--) {
        int n, m;
        cin >> n >> m;
        tt = 1, S = n * 2 + 1, T = n * 2 + 2;
        memset(hd, 0, sizeof hd);
        memset(ban, 0, sizeof ban);
        for (int i = 1; i <= n; ++i) link(S, i, 1);
        for (int i = 1; i <= n; ++i) link(n + i, T, 1);
        while (m--) {
            int u, v;
            cin >> u >> v;
            link(u, v + n, 1);
            link(v, u + n, 1);
            ban[u] = ban[v] = 1;
        }
        int cnt = 0;
        for (int i = 1; i <= n; ++i) cnt += !ban[i];
        int res = Dinic();
        if (cnt == 1 && res == n - 1) {
            res--;
            // cerr<<"!!\n";
        }
        // cerr<<res<<endl;
        cout << res * 2 - n << endl;
    }
    return 0;
}
 
 
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