Submission #980593

#	Time	Username	Problem	Language	Result	Execution time	Memory
980593		SirLemonMeringue	Cyberland (APIO23_cyberland)	C++17	100 / 100	290 ms	14408 KiB

cyberland

#include "cyberland.h"
#include <bits/stdc++.h>
using namespace std;
#define MAX_N 100010
#define INF 1e303

#include <vector>

vector<pair<int,int>> adj[MAX_N];
bool reachable[MAX_N];
double dist[MAX_N];

void dfs(int node, int specialNode){
    reachable[node] = true;
    if (node!=specialNode){
        for(auto a : adj[node]){
            if (!reachable[a.first]){
                dfs(a.first,specialNode);
            }
        }
    }
}

struct P {
    int dest;
    double dist;
    bool moved = true;
    bool operator< (P other) const {
        return dist > other.dist;
    }
};

double solve(int N, int M, int K, int H, vector<int> x, vector<int> y, vector<int> c, vector<int> arr) {
    //clear all adjacency lists and reachables and best dist
    for(int i=0;i<N;i++) adj[i].clear(), reachable[i]=false, dist[i]=INF;

    //remake all adjacencies
    for(int i=0;i<M;i++){
        adj[x[i]].push_back({y[i],c[i]});
        adj[y[i]].push_back({x[i],c[i]});
    }

    //run dfs to find all reachable nodes
    dfs(0,H);

    //if unreachable return
    if (!reachable[H]) return -1;
    reachable[H] = false;

    //run base dijkstra, sourced at reachable 0s and start
    priority_queue<P> todo;
    todo.push({0,0});
    for(int i=0;i<N;i++){
        if (reachable[i] && arr[i]==0){
            todo.push({i,0});
        }
    }

    while(!todo.empty()){
        P u = todo.top();
        todo.pop();
        if (u.dist < dist[u.dest]){
            dist[u.dest] = u.dist;
            if (u.dest != H){
                for(auto a : adj[u.dest]){
                    if (u.dist + a.second < dist[a.first]){
                        todo.push({a.first,u.dist+a.second});
                    }
                }
            }
        }
    }

    //printf("%lf %lf %lf\n",dist[0],dist[1],dist[2]);

    //run at most K further dijkstras, sourced at reachable 0s and reachable doubles (using half of best dist)
    for(int k=1;k<=K;k++){
        bool changed = false;
        //todo is already empty, so just add to it
        for(int i=0;i<N;i++){
            if (reachable[i]){
                if (arr[i]==0){
                    todo.push({i,0});
                    //printf("%d %lf\n",i,0);
                } else if (arr[i]==2){
                    todo.push({i,dist[i]/2,false});
                    //printf("%d %lf\n",i,dist[i]/2);
                }
            }
        }

        while(!todo.empty()){
            P u = todo.top();
            todo.pop();
            if (u.dist < dist[u.dest]){
                if (u.moved){
                    changed = true;
                    dist[u.dest] = u.dist;
                }
                if (u.dest != H){
                    for(auto a : adj[u.dest]){
                        if (u.dist + a.second < dist[a.first]){
                            todo.push({a.first,u.dist+a.second});
                        }
                    }
                }
            }
        }
        if (!changed) break;
    }
    
    return dist[H];
}

• Subtask 1: 5 / 5
• Subtask 2: 8 / 8
• Subtask 3: 13 / 13
• Subtask 4: 19 / 19
• Subtask 5: 7 / 7
• Subtask 6: 16 / 16
• Subtask 7: 29 / 29
• Subtask 8: 3 / 3