# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
1001698 | nomuluun | Race (IOI11_race) | C++14 | 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>
using namespace std;
int k, mn = INT_MAX;
vector<vector<int>> dp(200001, vector<int>(101, INT_MAX)); // sum I and ends at node v is the minimum of the paths
vector<pair<int, int>> adj[200001]; // save edges
vector<vector<pair<int, int>>> path;
bool vis[200005]={0};
vector<pair<int,int>>v[200005];
ll mi=INT_MAX; // keep the best paths of each weights
void DFS(int q, int dis, int hi, int ka){
int m=v[q].size();
if(dis==ka){
if(hi<mi)mi=hi;
}
for(int i=0; i<m; i++){
int k=v[q][i].first;
ll cost=v[q][i].second;
if(!vis[k]){
vis[k]=1;
DFS(k,dis+cost,hi+1,ka);
}
}
}
void dfs(int v, int p)
{
dp[v][0] = 0;
for (auto [i, w] : adj[v])
if (i != p)
dfs(i, v);
path.assign(k + 1, {});
for (auto [i, w] : adj[v])
{
if (i == p)
continue;
for (int j = w; j <= k; j++)
{
if (dp[i][j - w] == INT_MAX)
continue;
if (path[j].size() < 2)
path[j].push_back({dp[i][j - w] + 1, i}); // keep best two paths
else if (dp[i][j - w] + 1 < path[j][1].first)
path[j][1] = {dp[i][j - w] + 1, i}; // keep current path
if (path[j].size() == 2 && path[j][0].first > path[j][1].first)
swap(path[j][0], path[j][1]); // swap shortest path
dp[v][j] = min(dp[v][j], dp[i][j - w] + 1);
}
}
if (!path[k].empty())
mn = min(mn, path[k][0].first); // if there is any path which is exactly K
for (int i = 1; i < k; i++)
{
if (path[i].empty() || path[k - i].empty())
continue;
if (path[i][0].second != path[k - i][0].second)
mn = min(mn, path[i][0].first + path[k - i][0].first); // compare 2 best paths
else if (1 < path[k - i].size())
mn = min(mn, path[i][0].first + path[k - i][1].first); // compare 2 best paths if there is path over 1.
}
}
int best_path(int N, int K, int H[][2], int L[])
{
if(K<=100){
k = K;
for (int i = 0; i < N - 1; i++)
{
adj[H[i][0]].push_back({H[i][1], L[i]});
adj[H[i][1]].push_back({H[i][0], L[i]});
}
dfs(0, -1);
if (mn == INT_MAX)
return -1;
else
return mn;
}
else{
for(int i=0; i<N-1; i++){
v[H[i][0]].push_back({H[i][1], L[i]});
v[H[i][1]].push_back({H[i][0], L[i]});
}
for(int i=0; i<=N-1; i++){
for(int i=0; i<N; i++){
vis[i]=0;
}
vis[i]=1;
DFS(i,0,0,K); //ehleh oroi distance highway
}
if(mi==INT_MAX)return -1;
else return mi;
}
}