Submission #540752

#	Time	Username	Problem	Language	Result	Execution time	Memory
540752		Olympia	Valley (BOI19_valley)	C++17	0 / 100	365 ms	26424 KiB

valley

#include <vector>
#include <algorithm>
#include <iostream>
#include <set>
#include <cmath>
#include <map>
#include <random>
#include <cassert>
#include <ctime>
#include <cstdlib>
#include <queue>
#include <limits.h>
using namespace std;
class Tree {
private:
    int root;
    vector<vector<pair<int,int>>> adj; //node, weight
    vector<int> parent;
    vector<int> depth;
    map<pair<int,int>,int> weight;
    vector<bool> isVillage;
    vector<int> sub, pre, post;
public:
    Tree (int N, int root) {
        adj.resize(N);
        this->root = root;
        parent.resize(N);
        depth.resize(N);
        isVillage.assign(N, false);
        sub.resize(N);
        pre.resize(N), post.resize(N);
    }
    void add_edge (int u, int v, int w) {
        adj[u].push_back({v, w});
        adj[v].push_back({u, w});
        weight[{u, v}] = weight[{v, u}] = w;
    }
    void update_village (int u) {
        isVillage[u] = true;
    }
    int cntr = 0;
    void dfs (int curNode, int prevNode) {
        parent[curNode] = prevNode;
        sub[curNode] = -1;
        pre[curNode] = cntr++;
        for (pair<int,int> p: adj[curNode]) {
            if (p.first != prevNode) {
                dfs(p.first, curNode);
                if (sub[p.first] != -1) {
                    if (sub[curNode] == -1) sub[curNode] = INT_MAX;
                    sub[curNode] = min(sub[p.first] + weight[{curNode, p.first}], sub[curNode]);
                }
            }
        }
        if (curNode == root) {
            depth[curNode] = 0;
        } else {
            depth[curNode] = depth[prevNode] + weight[{curNode, prevNode}];
        }
        if (isVillage[curNode]) {
            sub[curNode] = 0;
        }
        post[curNode] = cntr++;
    }
    bool isAncestor (int a, int b) {
        //is a an ancestor of b?
        return (pre[a] <= pre[b] && post[a] >= post[b]);
    }
    int chmin (int a, int b) {
        if (a == -1) return b;
        if (b == -1) return a;
        return min(a, b);
    }
    void query (int a1, int a2, int b) {
        if (parent[a1] != a2) {
            swap(a1, a2);
        }
        //parent[a1] = a2
        if (!isAncestor(a1, b)) {
            cout << "escaped\n";
            return;
        }
        int x = b;
        int ans = -1;
        int delta = 0;
        while (x != a2) {
            //cout << b << " " << x << " " << sub[x] << " " << abs(depth[x] - depth[b]) << '\n';
            if (sub[x] != -1) {
                ans = chmin(ans, sub[x] + delta);
            }
            delta += weight[{x, parent[x]}];
            x = parent[x];
        }
        if (ans == -1) {
            cout << "oo\n";
            return;
        }
        cout << ans << '\n';
    }
    void read () {
        dfs(root, -1);
    }
};
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int N, S, Q, E;
    cin >> N >> S >> Q >> E;
    E--;
    Tree myTree(N, E);
    vector<pair<int,int>> edges;
    for (int i = 0; i < N - 1; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        u--, v--;
        edges.emplace_back(u, v);
        myTree.add_edge(u, v, w);
    }
    while (S--) {
        int x; cin >> x; x--;
        myTree.update_village(x);
    }
    myTree.read();
    while (Q--) {
        int u, v;
        cin >> u >> v;
        u--, v--;
        myTree.query(edges[u].first, edges[u].second, v);
    }
}

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