Submission #961104

#	Time	Username	Problem	Language	Result	Execution time	Memory
961104		okkoo	Race (IOI11_race)	C++17	100 / 100	291 ms	35652 KiB

race

#include <iostream>
#include <vector>
#include <queue>
#include <string.h>
using namespace std;
#define fastIO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

const int mxn = 2e5;
vector<vector<pair<int, int> > > adj(mxn+1, vector<pair<int, int> >());
int K;
int ans = 1e9;
bool processed[mxn+1];
int sz[mxn+1];
vector<int> lengths(mxn*5+1, 1e9);

int getSize(int node, int p){
    sz[node] = 1;
    for(pair<int, int> tmp: adj[node]){
        int to = tmp.first;
        if(!processed[to] && to!=p) sz[node] += getSize(to, node);
    }
    return sz[node];
}

int getCentroid(int node, int p, int mxSize){
    for(pair<int, int> tmp: adj[node]){
        int to = tmp.first; 
        if(!processed[to] && to!=p && sz[to] > mxSize) return getCentroid(to, node, mxSize);
    }
    return node;
}

queue<pair<int, int> > q;
queue<int> L;

void dfs(int node, int p, int edgeLen, int edgeCnt){
    if(K < edgeLen) return;
    ans = min(ans, lengths[K-edgeLen] + edgeCnt);
    q.push({edgeLen, edgeCnt});
    L.push(edgeLen);
    for(pair<int, int> tmp: adj[node]){
        int to = tmp.first;
        if(!processed[to] && to!=p) dfs(to, node, edgeLen + tmp.second, edgeCnt+1);
    }
    if(!p){
        while(!q.empty()){
            lengths[q.front().first] = min(lengths[q.front().first], q.front().second);
            q.pop();
        }
    }
}

void centroidDecomposition(int node){
    int centroid = getCentroid(node, 0, getSize(node, 0)/2);
    processed[centroid] = 1;
    lengths[0] = 0;
    for(pair<int, int> tmp: adj[centroid]){
        int to = tmp.first;
        if(!processed[to]) dfs(to, 0, tmp.second, 1);
    }
    while(!L.empty()){
        lengths[L.front()] = 1e9;
        L.pop();
    }
    for(pair<int, int> tmp: adj[centroid]){
        int to = tmp.first;
        if(!processed[to]) centroidDecomposition(to);
    }
}

int best_path(int n, int k, int h[][2], int l[]){
    fastIO;
    K = k;
    for(int i=0; i<n-1; i++){
        h[i][0]++; h[i][1]++;
        adj[h[i][0]].push_back({h[i][1], l[i]});
        adj[h[i][1]].push_back({h[i][0], l[i]});
    }

    centroidDecomposition(1);

    return (ans == 1e9 ? -1 : ans);
}

// int main(){
//     int n, k;
//     cin >> n >> k;
//     int h[n-1][2], l[n-1];
//     for(int i=0; i<n-1; i++){
//         cin >> h[i][0] >> h[i][1];
//     }
//     for(int i=0; i<n-1; i++){
//         cin >> l[i];
//     }
//     cout << best_path(n, k, h, l) << '\n';
// }

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 57 / 57