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