Submission #1107216

#	Time	Username	Problem	Language	Result	Execution time	Memory
1107216		dzhoz0	Race (IOI11_race)	C++17	100 / 100	362 ms	88136 KiB

race

/*
    ghmt the cutie :3
          UwU
*/


#include "race.h"
#include <bits/stdc++.h>
using namespace std;

#define INF 1e9
#define f first
#define s second
#define pii pair<int, int>
#define vi vector<int>


const int MAXN = 2e5;
int n, k;
vector<pii> g[MAXN + 5];
int h[MAXN + 5], d[MAXN + 5];
int res = INF;
map<int, int> mp[MAXN + 5];
void pre_dfs(int u, int par = -1) {
    mp[u][d[u]] = h[u];
    for(auto [v, w] : g[u]) {
        if(v == par) continue;
        h[v] = h[u] + 1;
        d[v] = d[u] + w;
        pre_dfs(v, u);
    }
}

// mp[u][w1]

void dfs(int u, int par = -1) {
    for(auto [v, w] : g[u]) {
        if(v == par) continue;
        dfs(v, u);
        if(mp[u].size() < mp[v].size()) swap(mp[u], mp[v]);
        for(auto it : mp[v]) {
            int need = (k + 2 * d[u]) - it.f;
            if(mp[u].find(need) != mp[u].end()) {
                // cout << u << ' ' << v << ' ' << it.f << ' ' << k << ' ' <<  it.s + mp[u][need] - 2 * d[u] << '\n';
                res = min(res, it.s + mp[u][need] - 2 * h[u]);
            } 

        }
        for(auto it : mp[v]) {
            if(mp[u].find(it.f) != mp[u].end()) mp[u][it.f] = min(mp[u][it.f], it.s); 
            else mp[u][it.f] = it.s;
        }
    }
}

int solve() {
    memset(h, 0, sizeof(h));
    memset(d, 0, sizeof(d));
    pre_dfs(1, 1);
    // for(int i = 1; i <= n; i++) cout << i << ' ' << h[i] << '\n'; cout << '\n';
    dfs(1, 1);
    if(res == INF) return -1;
    else return res;
}


int best_path(int N, int K, int H[][2], int L[])
{
    // cout << "saygex\n";
    n = N, k = K;
    for(int i = 0; i < n - 1; i++) {
        int u = H[i][0], v = H[i][1], w = L[i];
        u++, v++;
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    return solve();
}

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