Submission #474307

#	Time	Username	Problem	Language	Result	Execution time	Memory
474307		hidden1	Valley (BOI19_valley)	C++14	100 / 100	283 ms	50508 KiB

valley

#include <bits/stdc++.h>
using namespace std;
//#pragma GCC optimize ("O3")
//#pragma GCC target ("sse4")
#define endl "\n"
typedef long long ll;
template<class T, class T2> inline ostream &operator <<(ostream &out, const pair<T, T2> &x) { out << x.first << " " << x.second; return out;}
template<class T, class T2> inline istream &operator >>(istream &in, pair<T, T2> &x) { in >> x.first >> x.second; return in;}
template<class T, class T2> inline bool chkmax(T &x, const T2 &y) { return x < y ? x = y, 1 : 0; }
template<class T, class T2> inline bool chkmin(T &x, const T2 &y) { return x > y ? x = y, 1 : 0; }
const ll mod = 1e16 + 7;
#define debug(...) cout << "Line: " << __LINE__ << endl; \
    printDebug(", "#__VA_ARGS__, __VA_ARGS__)
template <typename T>
void printDebug(const char* name, T&& arg1) { cout << (name + 2) << " = " << arg1 << endl; }
template <typename T, typename... T2>
void printDebug(const char* names, T&& arg1, T2&&... args) {
    const char* end = strchr(names + 1, ',');
    cout.write(names + 2, end - names - 2) << " = " << arg1 << endl;
    printDebug(end, args...);
}

const ll MAX_N = 1e5 + 10, LOG = 20;
ll par[MAX_N][LOG], mn[MAX_N][LOG];
ll dp[MAX_N], help_dp[MAX_N];
ll d[MAX_N], in[MAX_N], out[MAX_N], tme = -1;
vector<pair<ll, ll> > g[MAX_N];
ll n, s, q, e;
bool good[MAX_N];

void dfs(ll x, ll p) {
    dp[x] = help_dp[x] = mod;
    in[x] = out[x] = ++ tme;

    for(auto it : g[x]) {
        if(it.first == p) {continue;}
        d[it.first] = d[x] + it.second;

        dfs(it.first, x);

        chkmin(dp[x], help_dp[it.first] - 2 * d[x]);
        chkmin(help_dp[x], help_dp[it.first]);
        out[x] = out[it.first];
    }

    if(good[x]) {
        dp[x] = -d[x];
        help_dp[x] = d[x];
    }
}

void lca_calc(ll x, ll p) {
    par[x][0] = p;
    mn[x][0] = min(dp[x], dp[p]);
    for(ll i = 1; i < LOG; i ++) {
        par[x][i] = par[par[x][i - 1]][i - 1];
        mn[x][i] = min(mn[par[x][i - 1]][i - 1], mn[x][i - 1]);
    }
    for(auto it : g[x]) {
        if(it.first == p) {continue;}
        lca_calc(it.first, x);
    }
}

ll ans(ll x, ll y) {
    ll ret = dp[x];
    for(ll i = LOG - 1; i >= 0; i --) {
        if(d[par[x][i]] >= d[y]) {
            chkmin(ret, mn[x][i]);
            x = par[x][i];
        }
    }
    return ret;
}

pair<ll, ll> edges[MAX_N];

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    cin >> n >> s >> q >> e;
    for(ll i = 0; i < n - 1; i ++) {
        ll a, b, c;
        cin >> a >> b >> c;
        g[a].push_back({b, c});
        g[b].push_back({a, c});
        edges[i + 1] = {a, b};
    }
    for(ll i = 0; i < s; i ++) {
        ll a;
        cin >> a;
        good[a] = true;
    }
    dfs(e, 0);
    for(int i = 0; i < LOG; i ++) {
        mn[1][i] = mod;
        mn[0][i] = mod;
    }
    dp[0] = mod;
    lca_calc(e, 0);

    for(ll i = 0; i < q; i ++) {
        ll a, ind;
        cin >> ind >> a;
        ll lower;
        if(d[edges[ind].first] > d[edges[ind].second]) {
            lower = edges[ind].first;
        } else {
            lower = edges[ind].second;
        }
        if(in[lower] <= in[a] && in[a] <= out[lower]) {
            ll best_lca = ans(a, lower);
            if(best_lca >= 2e15) {
                cout << "oo" << endl;
            } else {
                cout << best_lca + d[a] << endl;
            }
        } else {
            cout << "escaped" << endl;
        }
    }
    return 0;
}

/*
5 2 100 1
1 2 1
2 3 2
3 4 3
4 5 2
3 5
1 5
*/

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