Submission #1028489

#	Time	Username	Problem	Language	Result	Execution time	Memory
1028489		Thanhs	Mousetrap (CEOI17_mousetrap)	C++14	25 / 100	538 ms	99664 KiB

mousetrap

#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define int long long
// #define double long double
 
#define endl '\n'
#define fastIO ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
#define setmin(x, y) x = min((x), (y))
#define setmax(x, y) x = max((x), (y))
#define sqr(x) ((x) * (x))
#define fi first
#define se second
 
// mt19937 hdp(chrono::high_resolution_clock::now().time_since_epoch().count());
// int rand(int l, int r){return l + ((hdp() % (r - l + 1)) + r - l + 1) % (r - l + 1);}
 
const int NM = 1e6 + 5;
const int mod = 1e6 + 3;
const int inf = 1e9 + 1;

vector<int> g[NM];
int n, t, m, w[NM], dep[NM], par[NM];

void dfs(int u = t, int p = 0)
{
    int be = 0, sb = 0;
    for (auto v : g[u])
    {
        if (v == p)
            continue;
        dep[v] = dep[u] + 1;
        par[v] = u;
        dfs(v, u);
        if (be < w[v])
        {
            sb = be;
            be = w[v];
        }
        else if (sb < w[v])
            sb = w[v];
    }
    if (g[u].size() - !!p == 0)
        w[u] = 0;
    else if (g[u].size() - !!p == 1)
        w[u] = 1;
    else 
        w[u] += sb + g[u].size() - !!p;
}

signed main()
{
    if (fopen("in.txt", "r")) {
        freopen("in.txt","r",stdin);
        freopen("out.txt","w",stdout);
    }
    fastIO
    cin >> n >> t >> m;
    for (int i = 2; i <= n; i++)
    {
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    dfs();
    cout << w[m];
}

Compilation message (stderr)

mousetrap.cpp: In function 'int main()':
mousetrap.cpp:55:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   55 |         freopen("in.txt","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~
mousetrap.cpp:56:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   56 |         freopen("out.txt","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 20
• Subtask 2: 25 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35