Submission #1282186

#	Time	Username	Problem	Language	Result	Execution time	Memory
1282186		dex111222333444555	Valley (BOI19_valley)	C++20	36 / 100	3094 ms	17592 KiB

valley

#include <bits/stdc++.h>
#define all(v) begin(v), end(v)
template<class X, class Y> bool minimize(X &x, const Y &y){return x > y ? x = y, 1: 0;}
template<class X, class Y> bool maximize(X &x, const Y &y){return x < y ? x = y, 1: 0;}
using namespace std;
const int MAXN = 1e5 + 5, infINT = 1e9 + 389;
const long long inf = 1e18 + 3818;

struct edge{
    int u, v, w;

    edge(int _u = 0, int _v = 0, int _w = 0):
        u(_u), v(_v), w(_w) {};

    int other(int x){
        return u ^ v ^ x;
    }
};

int numNode, numShop, numQuery, root, chain[MAXN], h[MAXN], sta[MAXN], fin[MAXN], sz[MAXN], par[MAXN];
long long dist[MAXN], best[MAXN];
bool shop[MAXN];
edge e[MAXN];
vector<int> adj[MAXN];

struct segmentTree{
    int n;
    vector<long long> mi;

    segmentTree(int _n = 0): n(_n){
        mi.assign(n << 1 | 1, inf);
    }

    void update(int pos, long long x){
        pos--; pos += n;
        mi[pos] = x;
        while(pos > 1){
            pos >>= 1;
            minimize(mi[pos], mi[pos << 1]);
            minimize(mi[pos], mi[pos << 1 | 1]);
        }
    }

    long long get(int l, int r){
        l--;
        l += n; r += n;
        long long res = inf;
        while(l < r){
            if (l & 1) minimize(res, mi[l++]);
            if (r & 1) minimize(res, mi[--r]);
            l >>= 1; r >>= 1;
        }
        return res;
    }
} myIt;

void dfsInit(int u){
    sz[u] = 1;
    for(int id: adj[u]){
        int v = e[id].other(u);
        if (v == par[u]) continue;
        par[v] = u; h[v] = h[u] + 1;
        dist[v] = dist[u] + e[id].w;
        dfsInit(v);
        sz[u] += sz[v];
    }
    sort(all(adj[u]), [&](const int &a, const int &b){
         return (a == par[u] ? INT_MIN: sz[a]) > (b == par[u] ? INT_MIN: sz[b]);
    });
}

void dfsMark(int u, bool isHeavy = 0){
    sta[u] = ++sta[0];
    chain[u] = (isHeavy ? chain[par[u]]: u);
    if (shop[u]) best[u] = 0;
    for(int id: adj[u]){
        int v = e[id].other(u);
        if (v == par[u]) continue;
        dfsMark(v, v == e[adj[u][0]].other(u));
        minimize(best[u], best[v] + e[id].w);
    }
    fin[u] = sta[0];
}

bool check(int R, int u){
    return sta[u] <= sta[R] && sta[R] <= fin[u];
}

long long getHLD(int u, int p){
    long long res = inf;
    while(chain[u] != chain[p]){
        minimize(res, myIt.get(sta[chain[u]], sta[u]));
        u = par[chain[u]];
    }
    minimize(res, myIt.get(sta[p], sta[u]));
    return res;
}

void input(){
    cin >> numNode >> numShop >> numQuery >> root;
    int u, v, w;
    for(int i = 1; i < numNode; i++){
        cin >> u >> v >> w;
        adj[u].push_back(i);
        adj[v].push_back(i);
        e[i] = edge(u, v, w);
    }
    for(int i = 1; i <= numShop; i++){
        int x; cin >> x;
        shop[x] = 1;
    }
}

void solve(){
    for(int i = 1; i <= numNode; i++) best[i] = inf;
    dfsInit(root);
    dfsMark(root);
    myIt = segmentTree(numNode);
    for(int i = 1; i <= numNode; i++){
        if (dist[i] < inf && best[i] < inf) myIt.update(sta[i], best[i] - dist[i]);
    }
    while(numQuery--){
        int id, R;
        cin >> id >> R;
        int u = e[id].u, v = e[id].v;
        if (h[u] < h[v]) swap(u, v);
        if (!check(R, u)) cout << "escaped\n";
        else{
            long long x = getHLD(R, u);
            long long res = dist[R] + x;
            if (res < inf) cout << res << '\n';
            else cout << "oo\n";
        }
    }
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen("test.inp", "r")){
        freopen("test.inp", "r", stdin);
        freopen("test.out", "w", stdout);
    }
    input();
    solve();
}

Compilation message (stderr)

valley.cpp: In function 'int main()':
valley.cpp:140:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  140 |         freopen("test.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:141:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  141 |         freopen("test.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 0 / 23
• Subtask 4: 0 / 41