Submission #1000834

#	Time	Username	Problem	Language	Result	Execution time	Memory
1000834		ALTAKEXE	Race (IOI11_race)	C++17	31 / 100	352 ms	262144 KiB

race

#include <bits/stdc++.h>
#include "race.h"
using namespace std;
 
#define ff  first
#define ss  second
#define pii pair<int, int>
 
int k, mn = INT_MAX;
 
vector<vector<int>> dp;
 
vector<vector<pii>> v, E;
 
void dfs(int x, int p = - 1) {
    dp[x][0] = 0;
 
    for (auto [i, w] : E[x])
        if (i != p) dfs(i, x);
 
    v.assign(k + 1, {});
    for (auto [i, w] : E[x]) {
        if (i == p) continue;
 
        for (int j = w; j <= k; j++) {
            if (dp[i][j - w] == INT_MAX) continue;
 
            if ((int)v[j].size() < 2) v[j].push_back({dp[i][j - w] + 1, i});
            else if (dp[i][j - w] + 1 < v[j][1].ff) v[j][1] = {dp[i][j - w] + 1, i};
            
            if ((int)v[j].size() == 2 && v[j][0].ff > v[j][1].ff) swap(v[j][0], v[j][1]);
 
            dp[x][j] = min(dp[x][j], dp[i][j - w] + 1);
        }
    }
 
    if (!v[k].empty()) mn = min(mn, (int)v[k][0].ff);
    for (int i = 1; i < k; i++) {
        if (v[i].empty() || v[k - i].empty()) continue;
 
        if (v[i][0].ss != v[k - i][0].ss) mn = min(mn, v[i][0].ff + v[k - i][0].ff);
        else if (1 < (int)v[k - i].size()) mn = min(mn, v[i][0].ff + v[k - i][1].ff);
    }
}
 
int best_path(int N, int K, int H[][2], int L[]) {
    k = K;
 
    E.assign(N, {});
    for (int i = 0; i < N - 1; i++) {
        E[H[i][0]].push_back({H[i][1], L[i]});
        E[H[i][1]].push_back({H[i][0], L[i]});
    }
 
    dp.assign(N, vector<int>(k + 1, INT_MAX));
    dfs(0);
 
    return (mn == INT_MAX ? -1 : mn);
}

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