一场codeforce比赛

,
就这样我们失去了名额。这场 codeforce 可以说是比较简单的一场了，自我感觉还有三题可做。

题面

Problem F

Keeping On Track

思路

DFS + 贪心

AC代码

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#define others
#ifdef poj
#include <iostream>
#include <cstring>
#include <cmath>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <string>
#endif // poj
#ifdef others
#include <bits/stdc++.h>
#endif // others
//#define file
#define all(x) x.begin(), x.end()
using namespace std;
const double eps = 1e-8;
int dcmp(double x)
{
    if (fabs(x) <= eps)
        return 0;
    return (x > 0) ? 1 : -1;
};
typedef long long LL;
void umax(LL &a, LL b) { a = max(a, b); }
void umin(LL &a, LL b) { a = min(a, b); }
#ifdef backup
cccc
#endif // backup

    /*33+x
29+x
*/
    void
    file()
{
    freopen("out.txt", "r", stdin);
    freopen("1.txt", "w", stdout);
}

namespace solver
{
const int maxn = 10001;
int n;
vector<int> G[maxn];
int sz[maxn];
LL maxv = 0, id = 0;
void dfs(int u, int fa)
{
    sz[u] = 1;
    vector<int> V;
    int sum = 0;
    for (int i = 0; i < G[u].size(); i++)
    {
        int v = G[u][i];
        if (v == fa)
            continue;
        dfs(v, u);
        V.push_back(sz[v]);
        sum += sz[v];
        sz[u] += sz[v];
    }
    int ff = n - sum;
    V.push_back(ff);
    LL res = 0;
    LL ss = 0;
    for (int i = 0; i < V.size(); i++)
    {
        //            cout<<V[i]<<" "<<u<<endl;
        res += ss * V[i];
        ss += V[i];
    }
    if (res > maxv)
    {
        maxv = res;
        id = u;
    }
}
void dfs2(int u, int fa)
{
    sz[u] = 1;
    int sum = 0;
    for (int i = 0; i < G[u].size(); i++)
    {
        int v = G[u][i];
        if (v == fa)
            continue;
        dfs2(v, u);
        sz[u] += sz[v];
    }
}
void solve()
{
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
    {
        int u, v;
        scanf("%d%d", &u, &v);
        G[u].push_back(v);
        G[v].push_back(u);
    }
    dfs(0, -1);
    dfs2(id, -1);
    LL ss = 0;
    vector<LL> V;
    for (int i = 0; i < G[id].size(); i++)
        V.push_back(sz[G[id][i]]);
    if (V.size() == 1)
    {
        cout << 0 << " " << 0 << endl;
    }
    else
    {
        sort(all(V));
        V[V.size() - 2] += V[V.size() - 1];
        LL ss = 0, res = 0;
        for (int i = 0; i < V.size() - 1; i++)
        {
            res += ss * V[i];
            ss += V[i];
        }
        cout << maxv << " " << res << endl;
    }
}
} // namespace solver

int main()
{
    //    file();
    solver::solve();
    return 0;
}

Problem G

A Question of Ingestion

Problem J

Workout for a Dumbbell

参考博客

大佬博客1