Submission #617108

#	Time	Username	Problem	Language	Result	Execution time	Memory
617108		thezomb1e	Mousetrap (CEOI17_mousetrap)	C++17	0 / 100	313 ms	80280 KiB

mousetrap

//thatsramen

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define eb emplace_back
#define pb push_back
#define ft first
#define sd second
#define pi pair<int, int>
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define dbg(...) dbg_out(__VA_ARGS__)

using ll = long long;
using ld = long double;
using namespace std;
using namespace __gnu_pbds;

//Constants
const ll INF = 5 * 1e18;
const int IINF = 2 * 1e9;
// const ll MOD = 1e9 + 7;
const ll MOD = 998244353;
const ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const ld PI = 3.14159265359;

//Templates
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) {return os << '(' << p.first << ", " << p.second << ')';}
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) {os << '['; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << ']';}
void dbg_out() {cerr << endl;}
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << H << ' '; dbg_out(T...); }
template<typename T> void mins(T& x, T y) {x = min(x, y);}
template<typename T> void maxs(T& x, T y) {x = max(x, y);}
template<typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> using omset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;

//order_of_key(k): number of elements strictly less than k
//find_by_order(k): k-th element in the set

void setPrec() {cout << fixed << setprecision(15);}
void unsyncIO() {cin.tie(0)->sync_with_stdio(0);}
void setIn(string s) {freopen(s.c_str(), "r", stdin);}
void setOut(string s) {freopen(s.c_str(), "w", stdout);}
void setIO(string s = "") {
    unsyncIO(); setPrec();
    if(s.size()) setIn(s + ".in"), setOut(s + ".out");
}

// #define TEST_CASES

void solve() {
    int n, t, m;
    cin >> n >> t >> m;
    vector<vector<pi>> e(n + 5);
    for (int i = 0; i < n - 1; i++) {
        int u, v; cin >> u >> v;
        e[u].pb({v, i}); e[v].pb({u, i});
    }
    vector<bool> mark(n + 5, false);
    vector<int> path;
    function<bool(int, int)> dfs_path = [&](int f, int p) -> bool {
        if (f == t) { return true; }
        for (const auto &[to, id] : e[f]) {
            if (to == p) continue;
            if (dfs_path(to, f)) {
                path.pb(f);
                mark[id] = true;
                return true;
            }
        }
    };
    dfs_path(m, -1);
    vector<int> dp(n + 5, 0);
    function<void(int, int)> dfs = [&](int f, int p) {
        vector<pair<int, bool>> al;
        for (const auto &[to, id] : e[f]) {
            if (to == p) continue;
            dfs(to, f);
            al.pb({dp[to], mark[id]});
        }
        sort(rall(al));
        int sz = al.size();
        if (sz > 1) {
            dp[f] = al[1].ft + !al[1].sd + sz - 1;
        } else if (sz == 1) {
            dp[f] = !al[0].sd;
        }
    };
    dfs(m, -1);
    cout << dp[m];
}

int main() {
    setIO();

    int tt = 1;
    #ifdef TEST_CASES
        cin >> tt;
    #endif

    while (tt--) 
        solve();

    return 0;
}

Compilation message (stderr)

mousetrap.cpp: In function 'void setIn(std::string)':
mousetrap.cpp:44:30: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   44 | void setIn(string s) {freopen(s.c_str(), "r", stdin);}
      |                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
mousetrap.cpp: In function 'void setOut(std::string)':
mousetrap.cpp:45:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   45 | void setOut(string s) {freopen(s.c_str(), "w", stdout);}
      |                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
mousetrap.cpp: In lambda function:
mousetrap.cpp:73:5: warning: control reaches end of non-void function [-Wreturn-type]
   73 |     };
      |     ^

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