| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 984163 | stdfloat | Race (IOI11_race) | C++17 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
#include "race.h"
#include "grader.cpp"
using namespace std;
using ll = long long;
#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[]) {
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]});
}
if (N <= (int)1e3) {
for (int i = 0; i < N; i++) {
queue<int> q;
vector<int> cnt(N);
vector<ll> dis(N, -1);
q.push(i); dis[i] = 0;
while (!q.empty()) {
int x = q.front(); q.pop();
for (auto [j, w] : E[x]) {
if (dis[j] == -1) {
q.push(j);
cnt[j] = cnt[x] + 1;
dis[j] = dis[x] + w;
}
}
}
for (int j = 0; j < N; j++)
if (dis[j] == K) mn = min(mn, cnt[j]);
}
}
else {
k = K;
dp.assign(N, vector<int>(k + 1, INT_MAX));
dfs(0);
}
return (mn == INT_MAX ? -1 : mn);
}