Submission #982198

#	Time	Username	Problem	Language	Result	Execution time	Memory
982198		kh0i	Valley (BOI19_valley)	C++17	100 / 100	182 ms	51236 KiB

valley

#include "bits/stdc++.h"
using namespace std;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...)
#endif

using ll = long long;
using pii = pair<int, int>;

#define F first
#define S second
#define sz(x) (int)((x).size())
#define all(x) (x).begin(), (x).end()

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll get_rand(ll l, ll r) {
    assert(l <= r);
    return uniform_int_distribution<ll> (l, r)(rng);
}

const int N = 1e5 + 3;
const int LG = 17;

int n, s, q, e;
vector<pair<int, ll>> g[N];
int u[N], v[N];
ll w[N];
bool sh[N];

int tin[N], tout[N], timer;
ll f[N], dep[N], mn[N];
int h[N];
ll st[LG + 1][N], up[LG + 1][N];

void dfs(int u, int pre = -1){
    f[u] = (sh[u] ? 0 : 1e16);
    tin[u] = ++timer;
    for(auto [v, w] : g[u]){
        if(v == pre)
            continue;
        dep[v] = dep[u] + w;
        h[v] = h[u] + 1;
        dfs(v, u);
        f[u] = min(f[u], f[v] + w);
    }
    tout[u] = timer;
    mn[u] = f[u] - dep[u];
}

void dfs_st(int u, int pre = -1){
    for(auto [v, w] : g[u]){
        if(v == pre)
            continue;

        st[0][v] = mn[v];
        up[0][v] = u;

        for(int k = 1; k <= LG; ++k){
            up[k][v] = up[k - 1][up[k - 1][v]];
            st[k][v] = min(st[k - 1][v], st[k - 1][up[k - 1][v]]);
        }

        dfs_st(v, u);
    }
}

void solve(){
    cin >> n >> s >> q >> e;
    for(int i = 1; i < n; ++i){
        cin >> u[i] >> v[i] >> w[i];
        g[u[i]].push_back({v[i], w[i]});
        g[v[i]].push_back({u[i], w[i]});
    }
    for(int i = 1; i <= s; ++i){
        int x;
        cin >> x;
        sh[x] = 1;
    }

    dfs(e);
    dfs_st(e);

    while(q--){
        int i, r;
        cin >> i >> r;
        int x = u[i], y = v[i];
        if(h[x] < h[y])
            swap(x, y);

        if(tin[x] <= tin[r] and tin[r] <= tout[x]){
            int k = h[r] - h[x] + 1;
            ll dep_r = dep[r];
            ll mn_d = 1e16;

            for(int i = 0; (1 << i) <= k; ++i)
                if(k & (1 << i))
                   mn_d = min(mn_d, st[i][r]), r = up[i][r];

            if(mn_d > 1e15)
                cout << "oo" << '\n';
            else
                cout << dep_r + mn_d << '\n';
        }
        else
            cout << "escaped" << '\n';
    }    
}

int32_t main() {
    cin.tie(nullptr)->sync_with_stdio(0);
    #define task "troll"
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    int test = 1;
//    cin >> test;
    for(int i = 1; i <= test; ++i){
//        cout << "Case #" << i << ": ";
        solve();
    }
    #ifdef LOCAL
        cerr << "\n[Time]: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
    #endif
    return 0;
}

Compilation message (stderr)

valley.cpp: In function 'int32_t main()':
valley.cpp:116:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  116 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:117:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  117 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41