Submission #1279049

#	Time	Username	Problem	Language	Result	Execution time	Memory
1279049		tsengang	Race (IOI11_race)	C++17	100 / 100	1394 ms	75472 KiB

race

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define ertunt return
#define vodka void
set<pair<int,int>> v[200005];
vector<int> si(200005,0);
int n = 0;
int centroid(int x, int p){
    for(auto [u,w] : v[x]){
        if(u == p) continue;
        if(si[u]*2 > n) ertunt centroid(u,x);
    }
    ertunt x;
}
void calc(int x, int p){
    n++;
    si[x] = 1;
    for(auto [u,w] : v[x]){
        if(u == p) continue;
        calc(u,x);
        si[x] += si[u];
    }
}
int best_path(int N, int k, int h[][2], int l[]){
    for(ll i = 0; i < N - 1; i++){
        v[h[i][0]].insert({h[i][1], l[i]});
        v[h[i][1]].insert({h[i][0], l[i]});
    }
    int ans = 1e9;
    queue<int> q;
    q.push(0);
    vector<int> d(200005, 0);
    while(!q.empty()){
        int x = q.front();
        q.pop();
        n = 0;
        calc(x, -1);
        int root = centroid(x, -1);
        map<ll, int> dist, cur, clr;
        function<void(int,int,int)> dfs = [&](int x, int p, int depth){
            if(cur[d[x]] == 0) cur[d[x]] = depth;
            else cur[d[x]] = min(cur[d[x]], depth);
            for(auto [u, w] : v[x]){
                if(u != p){
                    d[u] = d[x] + w;
                    dfs(u, x, depth + 1);
                }
            }
        };
        for(auto [u, w] : v[root]){
            cur = clr;
            d[u] = w;
            dfs(u, root, 1);
            for(auto [mal, y] : cur){
                if(mal == k){
                    if(y > 0){
                        ans = min(ans, y);
                    }
                }
                else if(mal < k){
                    if(y > 0 && dist[k - mal] > 0){
                        ans = min(ans, y + dist[k - mal]);
                    }
                }
            }
            for(auto [w2, y] : cur){
                if(dist[w2] == 0) dist[w2] = y;
                else if(y > 0) dist[w2] = min(dist[w2], y);
            }
        }
        for(auto [u, w] : v[root]){
            v[u].erase({root, w});
            q.push(u);
        }
        v[root].clear();
    }
    if(ans == 1e9) ertunt -1;
    else ertunt ans;
}

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