Submission #888535

#	Time	Username	Problem	Language	Result	Execution time	Memory
888535		dwuy	Race (IOI11_race)	C++14	100 / 100	692 ms	45416 KiB

race

//#include "race.h"
#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;
typedef pair<int, int> pii;

const int MX = 200005;
int n, k, ans = MX;
int numC[MX];
bitset<MX> vist;
vector<pii> G[MX];

void calChild(int u, int p){
    numC[u] = 1;
    for(pii &tmp: G[u]){
        int v, c;
        tie(v, c) = tmp;
        if(v==p || vist[v]) continue;
        calChild(v, u);
        numC[u] += numC[v];
    }
}

int Centroid(int u, int p, const int &half){
    for(pii &tmp: G[u]){
        int v = tmp.fi;
        if(v == p || vist[v]) continue;
        if(numC[v] > half) return Centroid(v, u, half);
    }
    return u;
}

int dis[MX];
int node[MX];

int getmap(map<int, int> &mp, int value){
    auto itr = mp.find(value);
    if(itr == mp.end()) return 0;
    return itr->se;
}

int calValue(int u){
    map<int, int> mp;
    int res = MX;
    mp[0] = 1;
    for(pii &tmp: G[u]){
        int v, c;
        tie(v, c) = tmp;
        if (vist[v]) continue;
        vector<int> path;
        stack<pii> Q;
        Q.push({v, u});
        node[v] = 2;
        dis[v] = c;
        while(Q.size()){
            int u, p;
            tie(u, p) = Q.top();
            Q.pop();
            path.push_back(u);
            for(pii &tmp: G[u]){
                int v, c;
                tie(v, c) = tmp;
                if(vist[v] || v == p) continue;
                Q.push({v, u});
                dis[v] = dis[u] + c;
                node[v] = node[u] + 1;
            }
        }
        for(int vt: path) if(dis[vt]<=k){
            int gm = getmap(mp, k - dis[vt]);
            if(gm) res = min(res, gm + node[vt] - 1);
        }
        for(int vt: path) if(dis[vt]<=k){
            if(mp[dis[vt]]==0) mp[dis[vt]] = node[vt];
            else mp[dis[vt]] = min(mp[dis[vt]], node[vt]);
        }
    }
    return res;
}

void dwuy_simp_nvpu(int u){
    calChild(u, 0);
    u = Centroid(u, 0, numC[u]>>1);
    ans = min(ans, calValue(u));
    vist[u] = 1;
    for(pii &tmp: G[u]){
        int v = tmp.fi;
        if(!vist[v]) dwuy_simp_nvpu(v);
    }
}

int best_path(int N, int K, int H[][2], int L[]){
    n = N;
    k = K;
    for(int i=0; i<n-1; i++){
        int u = H[i][0];
        int v = H[i][1];
        int c = L[i];
        u++, v++;
        G[u].push_back({v, c});
        G[v].push_back({u, c});
    }
    dwuy_simp_nvpu(1);
    return ans==MX? -1 : ans - 1;
}

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