Submission #1180989

#	Time	Username	Problem	Language	Result	Execution time	Memory
1180989		jasonic	Dreaming (IOI13_dreaming)	C++20	32 / 100	60 ms	17592 KiB

dreaming

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

#define ll long long
#define fastIO cin.tie(0); ios::sync_with_stdio(false)

unordered_map<int, vector<pair<int, int>>> adjList;
bool vis[100005];
int d1[100005];
int d2[100005];
int farthest[100005];

void tryPush(set<int> &a, vector<int> &b, int x) {
    if(a.find(x) == a.end()) {
        a.emplace(x);
        b.push_back(x);
    }
}

void dp1(vector<int> &comp, int v, int p = -1) {

    comp.push_back(v);
    d1[v] = 0;

    int mxp1 = -1, mxp2 = -1;

    for(auto i : adjList[v]) if(i.first != p) {
        dp1(comp, i.first, v);
        int pl = d1[i.first] + i.second;
        d1[v] = max(d1[v], pl);
        if(mxp1 < pl) {
            mxp2 = mxp1;
            mxp1 = pl;
        } else if (mxp2 < pl) mxp2 = pl;
    }

    if(mxp2 != -1) {
        d2[v] = mxp1+mxp2;
    }
}

void dfs(set<int> &l, vector<int> &l2, int v, int p = -1) {
    bool leaf = true;

    for(auto i : adjList[v]) if(i.first != p) {
        leaf = false;
        dfs(l, l2, i.first, v);
    }

    if(leaf) tryPush(l, l2, v);
}

pair<int, int> solve(int r) {
    vector<int> connComp;
    set<int> leaves2;
    vector<int> leaves;

    dp1(connComp, r);
    dfs(leaves2, leaves, r);
    if(leaves.size() == 0) {
        tryPush(leaves2, leaves, connComp[0]); // size 0
    } else dfs(leaves2, leaves, leaves[0]);
    
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
    for(auto i : leaves) {pq.emplace(make_pair(0, i)); farthest[i] = 0;}
    int rad = 0;

    while(!pq.empty()) {
        pair<int, int> top = pq.top(); pq.pop();

        if(top.first < farthest[top.second]) continue; // if there was a faster route, skip this shorter one

        rad = max(rad, top.first);

        bool traversed = false;

        for(auto i : adjList[top.second]) {
            if(!vis[i.first]) {
                pq.emplace(make_pair(i.second + top.first, i.first));
                farthest[i.first] = max(farthest[i.first], i.second + top.first);
            }
        }
        vis[top.second] = true;
    }

    int d = 0;
    for(auto i : connComp) d = max(d, max(d1[i], d2[i]));

    return make_pair(d, rad);
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    
    for(int i = 0; i < N; i++) {
        vis[i] = false;
        d1[i] = -1;
        d2[i] = -1;
    }

    for(int i = 0; i < M; i++) {
        adjList[A[i]].push_back({B[i], T[i]});
        adjList[B[i]].push_back({A[i], T[i]});
    }

    vector<int> radii;
    vector<int> diams;
    int comps = 0;

    for(int i = 0; i < N; i++) {
        if(!vis[i]) {
            pair<int, int> ans = solve(i);
            diams.push_back(ans.first);
            radii.push_back(ans.second);
            comps++;
        }
    }

    sort(radii.begin(), radii.end(), greater<int>());
    sort(diams.begin(), diams.end(), greater<int>());
    
    if(comps == 1) {
        return diams[0];
    } else if (comps == 2) {
        return max(diams[0], radii[0] + radii[1] + L);
    } else {
        return max({diams[0], radii[0] + radii[1] + L, radii[1] + radii[2] + L + L});
    }
}

• Subtask 1: 14 / 14
• Subtask 2: 0 / 10
• Subtask 3: 0 / 23
• Subtask 4: 18 / 18
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23