#961095 (C++17) No.2677 Minmax Independent Set

• 問題: No.2677 Minmax Independent Set
• ユーザー: maeshun
• 提出日時: 2024-03-15 23:52:24
• 言語: C++17 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 523 ms / 2,000 ms
• コード長: 2,269 bytes
• コンパイル時間: 4,341 ms
• コンパイル使用メモリ: 254,872 KB
• 最終ジャッジ日時: 2025-02-20 06:30:55
• ジャッジサーバーID （参考情報）: judge2 / 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>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint;
using P = pair<ll,ll>;
using lb = long double;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif
int n;
vector<vector<int>> dp(2e5+5, vector<int>(2));
vector<int> ans(2e5+5);
vector<vector<int>> g(2e5+5);
int m;
//0 白 1 黒
vector<int> dfs(int u, int p=-1) {
    dp[u][0] = 0;
    dp[u][1] = 1;
    for(int v : g[u]){
        if(v==p) continue;
        dfs(v,u);
        dp[u][0] += max(dp[v][0], dp[v][1]);
        dp[u][1] += dp[v][0];
    }
    return dp[u];
};
void dfs2(int u, int p=-1){
    int N = g[u].size();
    if(N==0) return;
    vector<vector<int>> l(N, vector<int>(2));
    vector<vector<int>> r(N, vector<int>(2));
    ans[u] = 1;
    rep(i,N){
        ans[u] += dp[g[u][i]][0];
    }
    l[0][0] = dp[g[u][0]][0];
    l[0][1] = max(dp[g[u][0]][0],dp[g[u][0]][1]); 
    r[N-1][0] = dp[g[u][N-1]][0];
    r[N-1][1] = max(dp[g[u][N-1]][0],dp[g[u][N-1]][1]); 
    rep(i,N){
        int v = g[u][i];
        if(i-1>=0) {
            l[i][0] = l[i-1][0]+dp[v][0];
            l[i][1] = l[i-1][1]+max(dp[v][0],dp[v][1]);
        }
    }
    for(int i=N-1;i>=0;i--){
        int v = g[u][i];
        if(i+1<N) {
            r[i][0] = r[i+1][0]+dp[v][0];
            r[i][1] = r[i+1][1]+max(dp[v][0],dp[v][1]);
        }
    }
    rep(i,N){
        int v = g[u][i];
        if(v==p) continue;
        dp[u][0] = 0;
        dp[u][1] = 1;
        if(i-1>=0) {
            dp[u][1] += l[i-1][0];
            dp[u][0] += max(l[i-1][1],l[i-1][0]);
        }
        if(i+1<N) {
            dp[u][1] += r[i+1][0];
            dp[u][0] += max(r[i+1][1],r[i+1][0]);
        }
        dfs2(v, u);
    }
};
int main()
{
    cin >> n;
    if(n==1){
        cout<<1<<endl;
        return 0;
    }
    rep(i,n-1){
        int u, v;
        cin >> u >> v;
        --u;--v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    dfs(0);
    dfs2(0);
    cout<<*min_element(ans.begin(),ans.begin()+n)<<endl;
    return 0;
}
 
 
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