#961023 (C++17) No.2677 Minmax Independent Set

• 問題: No.2677 Minmax Independent Set
• ユーザー: zawakasu
• 提出日時: 2024-03-15 23:34:56
• 言語: C++17 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 487 ms / 2,000 ms
• コード長: 2,563 bytes
• コンパイル時間: 2,535 ms
• コンパイル使用メモリ: 205,932 KB
• 最終ジャッジ日時: 2025-02-20 06:10:35
• ジャッジサーバーID （参考情報）: judge2 / judge3

ファイルパターン	結果
sample	AC * 3
other	AC * 61

ソースコード

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#include <bits/stdc++.h>
namespace zawa {
using i16 = std::int16_t;
using i32 = std::int32_t;
using i64 = std::int64_t;
using i128 = __int128_t;
using u8 = std::uint8_t;
using u16 = std::uint16_t;
using u32 = std::uint32_t;
using u64 = std::uint64_t;
using usize = std::size_t;
} // namespace zawa
namespace zawa {
void SetFastIO() {
    std::cin.tie(nullptr)->sync_with_stdio(false);
}
void SetPrecision(u32 dig) {
    std::cout << std::fixed << std::setprecision(dig);
}
} // namespace zawa
using namespace zawa;
int main() {
    SetFastIO();
    int n; std::cin >> n;
    std::vector g(n, std::vector<int>{});
    for (int _{} ; _ < n - 1 ; _++) {
        int u, v; std::cin >> u >> v;
        u--; v--;
        g[u].emplace_back(v);
        g[v].emplace_back(u);
    }
    std::vector dp(n, std::vector<int>(2));
    auto dfs{[&](auto dfs, int v, int p) -> void {
        for (auto x : g[v]) if (x != p) dfs(dfs, x, v);
        for (auto x : g[v]) if (x != p) {
            dp[v][0] += std::max(dp[x][0], dp[x][1]);
        }
        dp[v][1] = 1;
        for (auto x : g[v]) if (x != p) {
            dp[v][1] += dp[x][0];
        }
        return;
    }};
    dfs(dfs, 0, -1);
    int ans{dp[0][1]};
    auto dfs2{[&](auto dfs, int v, int p, std::vector<int> propa) -> void {
        // std::cout << v + 1 << " -> " << propa[0] << ' ' << propa[1] << std::endl;
        assert((int)propa.size() == 2);
        int is{1};
        for (auto x : g[v]) is += (x == p ? propa[0] : dp[x][0]);
        ans = std::min(ans, is);
        int m{(int)g[v].size()};
        std::vector a(m, std::vector<int>(2));
        for (int i{} ; i < m ; i++) {
            a[i] = (g[v][i] == p ? propa : dp[g[v][i]]);
        }
        std::vector pref(m + 1, std::vector<int>(2));
        std::vector suf(m + 1, std::vector<int>(2));
        pref[0][1] = 0;
        for (int i{} ; i < m ; i++) {
            pref[i + 1][0] = pref[i][0] + std::max(a[i][0], a[i][1]);
            pref[i + 1][1] = pref[i][1] + a[i][0];
        }
        suf[m][1] = 0;
        for (int i{m - 1} ; i >= 0 ; i--) {
            suf[i][0] = suf[i + 1][0] + std::max(a[i][0], a[i][1]);
            suf[i][1] = suf[i + 1][1] + a[i][0];
        }
        for (int i{} ; i < m ; i++) {
            if (g[v][i] == p) continue;
            std::vector<int> next(2);
            next[0] = pref[i][0] + suf[i + 1][0];
            next[1] = pref[i][1] + suf[i + 1][1] + 1;
            dfs(dfs, g[v][i], v, next);
        }
    }};
    dfs2(dfs2, 0, -1, { 0, 0 });
    std::cout << ans << '\n';
}
 
 
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