Submission #1282314

#	Time	Username	Problem	Language	Result	Execution time	Memory
1282314		dex111222333444555	Valley (BOI19_valley)	C++20	100 / 100	129 ms	19232 KiB

valley

#include <bits/stdc++.h>
#define all(v) begin(v), end(v)
using namespace std;
template<class X, class Y> bool minimize(X &x, const Y &y){return x > y ? x = y, 1: 0;}
const int MAXN = 1e5 + 5;
const long long inf = 1e18 + 3;

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, h[MAXN], chain[MAXN], par[MAXN], sz[MAXN], sta[MAXN], fin[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;
        minimize(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 dfsLeaf(int u){
    sz[u] = 1;
    for(int id: adj[u]) if (e[id].other(u) != par[u]){
        int v = e[id].other(u);
        h[v] = h[u] + 1; dist[v] = dist[u] + e[id].w;
        par[v] = u;
        dfsLeaf(v);
        sz[u] += sz[v];
    }
    sort(all(adj[u]), [&](const int &idA, const int &idB){
       int a = e[idA].other(u);
       int b = e[idB].other(u);
       return (a == par[u] ? INT_MIN: sz[a]) > (b == par[u] ? INT_MIN: sz[b]);
    });
}

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

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;
}

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

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(){
    memset(best, 0x3f, sizeof best);
    dfsLeaf(root);
    dfsRoot(root);
    myIt = segmentTree(numNode);
    for(int u = 1; u <= numNode; u++) myIt.update(sta[u], best[u] - dist[u]);
    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 res = dist[R] + getHLD(R, u);
            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:133:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  133 |         freopen("test.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:134:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  134 |         freopen("test.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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