#961400 (C++23) No.2677 Minmax Independent Set

• 問題: No.2677 Minmax Independent Set
• ユーザー: kwm_t
• 提出日時: 2024-03-17 00:22:29
• 言語: C++23 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 104 ms / 2,000 ms
• コード長: 2,417 bytes
• コンパイル時間: 3,013 ms
• コンパイル使用メモリ: 257,012 KB
• 実行使用メモリ: 28,740 KB
• 最終ジャッジ日時: 2024-09-30 04:35:42
• 合計ジャッジ時間: 8,257 ms
• ジャッジサーバーID （参考情報）: judge3 / judge1

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>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint998244353;
//const int mod = 998244353;
//using mint = modint1000000007;
//const int mod = 1000000007;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
#include<vector>
#include<iostream> 
struct ReRooting {
    struct Edge {
        int to;
        Edge(int _to) :to(_to) {}
    };
    struct Data {
        int val0 = 0;
        int val1 = 0;
        int max = 0;
        Data(int val0 = 0, int val1 = 0, int max = 0) :val0(val0), val1(val1), max(max) {}
    };
    std::vector<std::vector<Edge>>g;
    std::vector<Data>dp;
    std::vector<Data>ans;
    int sz;
    ReRooting(int _sz) :sz(_sz) {
        g.resize(sz);
        dp.reserve(sz);
        ans.resize(sz);
    }
    void ReadGraph() {
        for (int i = 0; i < sz - 1; ++i) {
            int a, b; std::cin >> a >> b; a--; b--;
            g[a].push_back(b);
            g[b].push_back(a);
        }
    }
    Data merge(const Data &lh, const Data &rh) {
        Data ret = lh;
        ret.val0 += rh.max;
        ret.val1 += rh.val0;
        ret.max = max(ret.val0, ret.val1);
        return ret;
    }
    Data mergeR(const Data &lh, const Data &rh) {//★★
        Data ret = lh;
        ret.val0 -= rh.max;
        ret.val1 -= rh.val0;
        ret.max = max(ret.val0, ret.val1);
        return ret;
    }
    void dfs(int v, int p = -1) {
        Data val(0, 1, 1);
        for (auto e : g[v]) {
            if (p == e.to)continue;
            dfs(e.to, v);
            val = merge(val, dp[e.to]);
        }
        dp[v] = val;
    }
    void dfsR(int v, int p = -1) {
        ans[v] = dp[v];
        if (-1 != p)ans[v] = merge(ans[v], dp[p]);
        for (auto e : g[v]) {
            if (p == e.to)continue;
            dp[v] = mergeR(ans[v], dp[e.to]);
            dfsR(e.to, v);
        }
    }
    void output() {
        int val = sz;
        rep(i, sz)chmin(val, ans[i].val1);
        cout << val << endl;
    }
    void solve() {
        ReadGraph();
        dfs(0);
        dfsR(0);
        output();
    }
};
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n; cin >> n;
    ReRooting reroot(n);
    reroot.solve();
    return 0;
}
 
 
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