# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
917286 | Taxiradio | 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 n , k;
vector<vector<pair<int , int>>> g;
vector<int> s;
vector<bool> removed;
vector<int> cnt;
int ans = INT_MAX;
int sz;
void get_subtree_size(int p){
removed[p] = true;
s[p] = 1;
for(auto [x , y]:g[p]){
if(!removed[x]){
get_subtree_size(x);
s[p] += s[x];
}
}
removed[p] = false;
}
int get_centroid(int p){
removed[p] = true;
int centroid = p;
for(auto [x , y]:g[p]){
if(!removed[x] && s[x] > sz / 2){
centroid = get_centroid(x);
break;
}
}
removed[p] = false;
return centroid;
}
void dfs1(int p , int dis , int citys)
{
if(k >= dis){
ans = min(cnt[k-dis]+citys , ans);
}else return;
removed[p] = true;
for(auto [x , y]:g[p]){
if(!removed[x]){
dfs1(x , dis+y , citys+1);
}
}
removed[p] = false;
}
void dfs2(int p , int dis , int citys)
{
if(dis <= k)cnt[dis] = min(cnt[dis] , citys);else return;
removed[p] = true;
for(auto [x , y]:g[p]){
if(!removed[x]){
dfs2(x , dis+y , citys+1);
}
}
removed[p] = false;
}
void solve(int p){
cnt[0] = 0;
get_subtree_size(p);
sz = s[p];
int centroid = get_centroid(p);
removed[centroid] = true;
for(auto [x , y]: g[centroid]){
if(!removed[x]){
dfs1(x, y , 1);
dfs2(x, y , 1);
}
}
for(int i = 1; i < cnt.size(); i++){
cnt[i] = INT_MAX-n;
}
for(auto [x , y]: g[centroid]){
if(!removed[x]){
solve(x);
}
}
}
int main() {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> k;
g.resize(n);
s.resize(n);
removed.resize(n);
cnt.resize(1000 , INT_MAX-n);
for(int i = 0; i < n-1; i++){
int a , b ,c; cin >> a >> b >> c;
g[a].push_back({b , c});
g[b].push_back({a , c});
}
solve(0);
cout << ans;
}