| # | 제출 시각 | 아이디 | 문제 | 언어 | 결과 | 실행 시간 | 메모리 |
|---|---|---|---|---|---|---|---|
| 346023 | nextgenxing | 경주 (Race) (IOI11_race) | C++14 | 0 ms | 0 KiB |
이 제출은 이전 버전의 oj.uz에서 채점하였습니다. 현재는 제출 당시와는 다른 서버에서 채점을 하기 때문에, 다시 제출하면 결과가 달라질 수도 있습니다.
#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
#define f first
#define s second
#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define F0R(i, x) FOR(i, 0, x)
const int MAX_N = 200001;
const int MAX_K = 1000001;
const int INF = 0x3f3f3f3f;
void setIO(string name = "race2") {
ios_base::sync_with_stdio(0); cin.tie(0);
freopen((name+".in").c_str(), "r", stdin);
freopen((name+".out").c_str(), "w", stdout);
}
int n, k, ans = INF;
int sz[MAX_N], depth[MAX_N], dist[MAX_N], mins[MAX_K];
bitset<MAX_N> removed;
bitset<MAX_K> done;
vector<pii> tree[MAX_N];
queue<pii> q;
int dfs(int curr, int par = -1){
sz[curr] = 1;
for(pii child : tree[curr]){
if(child.f == par || removed[child.f]) continue;
sz[curr]+=dfs(child.f, curr);
}
return sz[curr];
}
int main(int argc, const char * argv[]) {
// setIO();
cin >> n >> k;
F0R(i, n-1){
int a, b, c; cin >> a >> b >> c;
tree[a].push_back({b, c});
tree[b].push_back({a, c});
}
queue<int> q2; q2.push(0);
while(!q2.empty()){
int cr = q2.front(); q2.pop();
int ms = dfs(cr), C; q.push({cr, -1});
while(!q.empty()){
bool flag = false;
int curr = q.front().f, par = q.front().s; q.pop();
for(pii child : tree[curr]){
if(child.f == par || removed[child.f]) continue;
if(sz[child.f]*2 > ms){
flag = true;
q.push({child.f, curr});
break;
}
}
if(!flag){
C = curr;
while(q.size()) q.pop();
}
}
depth[C] = 0, dist[C] = 0, q.push({C, -1});
while(!q.empty()){
int curr = q.front().f, par = q.front().s; q.pop();
for(pii child : tree[curr]){
if(child.f == par || removed[child.f]) continue;
depth[child.f] = depth[curr]+1;
dist[child.f] = dist[curr]+child.s;
q.push({child.f, curr});
}
}
done.reset();
mins[0] = 0; done[0] = 1;
for(pii x : tree[C]){
q.push({x.f, C});
while(!q.empty()){
int curr = q.front().f, par = q.front().s; q.pop();
if(dist[curr] > k) continue;
if(done[k-dist[curr]]) ans = min(ans, mins[k-dist[curr]]+depth[curr]);
for(pii child : tree[curr]){
if(child.f == par || removed[child.f]) continue;
q.push({child.f, curr});
}
} q.push({x.f, C});
while(!q.empty()){
int curr = q.front().f, par = q.front().s; q.pop();
if(dist[curr] > k) continue;
if(!done[dist[curr]]) mins[dist[curr]] = depth[curr];
else mins[dist[curr]] = min(mins[dist[curr]], depth[curr]);
done[dist[curr]] = 1;
for(pii child : tree[curr]){
if(child.f == par || removed[child.f]) continue;
q.push({child.f, curr});
}
}
}
removed[C] = 1;
for(pii x : tree[C])
if(!removed[x.f])
q2.push(x.f);
}
if(ans == INF) cout << -1 << endl;
else cout << ans << endl;
return 0;
}