Submission #1097230

#	Time	Username	Problem	Language	Result	Execution time	Memory
1097230		orcslop	Race (IOI11_race)	C++17	0 / 100	6 ms	14424 KiB

race

#include <bits/stdc++.h>
using namespace std;
using ll = long long; 
#define pb push_back
#define all(x) begin(x), end(x)
#define sz(x) (int) (x).size()
#define f first
#define s second
#define pii pair<int, int>
bool ckmin(int& a, int b){ return b < a ? a = b, true : false; }
bool ckmax(int& a, int b){ return b > a ? a = b, true : false; }

struct Highway{
    int a, b, w; 
}; 

const int N = 2e5 + 5; 

int n, k, ans = 1e9; 
ll c[N]; 
int d[N]; 
Highway h[N]; 
map<int, int> mp[N]; 
vector<pii> adj[N]; 

void dfs(int node, int prev, ll sum = 0, int dist = 0){
    c[node] = sum; 
    d[node] = dist; 
    mp[node][sum] = dist; 
    for(auto x : adj[node]){
        if(x.f == prev) continue; 
        dfs(x.f, node, sum + x.s, dist + 1); 
    }
}

void dfs2(int node, int prev){
    ll t = k + 2 * c[node]; 
    for(auto x : adj[node]){
        if(x.f == prev) continue; 
        dfs2(x.f, node); 
        if(sz(mp[x.f]) > sz(mp[node])) {
            swap(mp[x.f], mp[node]); 
        }
        for(auto y : mp[x.f]){
            if(mp[node].count(t - y.f)){
                ckmin(ans, mp[node][t - y.f] + y.s - 2 * d[node]); 
            }
        }
        for(auto y : mp[x.f]){
            if(!mp[node].count(y.f)){
                mp[node][y.f] = y.s; 
            }
            else{
                ckmin(mp[node][y.f], y.s); 
            }
        }
    }
}

int best_path(int n, int k, int edges[][2], int weights[]) {
    if (k == 1) { return 0; }
    for (int i = 0; i < n - 1; i++) {
        int u = edges[i][0];
        int v = edges[i][1];
        adj[u].pb({v, weights[i]});
        adj[v].pb({u, weights[i]});
    }
    dfs(0, -1); 
    dfs2(0, -1); 
    return (ans == 1e9 ? -1 : ans);
}

// int32_t main() {
//     cin.tie(0)->sync_with_stdio(0);
//     cin >> n >> k; 
//     for(int i = 0; i < n - 1; i++){
//         cin >> h[i].a >> h[i].b; 
//     }
//     for(int i = 0; i < n - 1; i++){
//         cin >> h[i].w; 
//     }
//     for(int i = 0; i < n - 1; i++){
//         adj[h[i].a].pb({h[i].b, h[i].w}); 
//         adj[h[i].b].pb({h[i].a, h[i].w}); 
//     }
//     dfs(0, -1); 
//     dfs2(0, -1); 
//     cout << (ans < 1e9 ? ans : -1) << '\n'; 
//     return 0; 
// }

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57