| # | 제출 시각 | 아이디 | 문제 | 언어 | 결과 | 실행 시간 | 메모리 |
|---|---|---|---|---|---|---|---|
| 985321 | tvladm2009 | Closing Time (IOI23_closing) | C++17 | 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 long long ll;
const int N = 2e5 + 7;
vector<pair<int, int>> g[N];
int ans = 0;
vector<ll> find_dist(int n, int x) {
vector<ll> dist(n, -1);
queue<int> q;
q.push(x);
dist[x] = 0;
while (!q.empty()) {
int u = q.front();
q.pop();
for (auto v : g[u]) {
if (dist[v.first] == -1) {
dist[v.first] = dist[u] + v.second;
q.push(v.first);
}
}
}
return dist;
}
int max_score(int n, int X, int Y, ll K, vector<int> U, vector<int> V, vector<int> W) {
for (int i = 0; i < n; ++i) {
g[i].clear();
}
ans = 0;
for (int i = 0; i < n - 1; ++i) {
g[U[i]].push_back(make_pair(V[i], W[i]));
g[V[i]].push_back(make_pair(U[i], W[i]));
}
vector<ll> distX = find_dist(n, X);
vector<ll> distY = find_dist(n, Y);
vector<ll> one(n, 0), two(n, 0);
for (int i = 0; i < n; ++i) {
one[i] = min(distX[i], distY[i]);
two[i] = max(distX[i], distY[i]);
}
one[X] = two[X];
one[Y] = two[Y];
two[X] = two[Y] = K + 1;
{
vector<ll> aux = one;
sort(aux.begin(), aux.end());
ll sum = 0;
for (int i = 0; i < n; ++i) {
if (sum + aux[i] <= K) {
ans++;
sum += aux[i];
}
}
if (distX[Y] + 1 > 2 * K) {
return ans;
}
}
vector<bool> counted(n, 0);
ll d = distX[Y], between = 0;
int cnt = 0;
for (int i = 0; i < n; ++i) {
if (distX[i] + distY[i] == d) {
between += one[i];
cnt++;
counted[i] = 1;
}
}
ll sum_other_two = 0;
vector<int> ord2;
for (int i = 0; i < n; ++i) {
if (i != X && i != Y) {
ord2.push_back(i);
}
}
sort(ord2.begin(), ord2.end(), [&](int x, int y) {
return two[x] < two[y];
});
int ptr = 0;
vector<int> ord1(n);
iota(ord1.begin(), ord1.end(), 0);
sort(ord1.begin(), ord1.end(), [&](int x, int y) {
return one[x] < one[y];
});
auto get_sum_other_one = [&](int twos, int ones) {
if (ones == 0) {
return 0LL;
}
ll sum = 0;
for (int i = 0; i < n; ++i) {
if (counted[ord1[i]] == 0) {
sum += one[ord1[i]];
ones--;
if (ones == 0) {
break;
}
}
}
return sum;
};
auto is_under = [&](int u, int v) {
if (v == X) {
return (distX[u] == distY[u] - distX[Y]);
}
if (v == Y) {
return (distY[u] == distX[u] - distY[X]);
}
};
int extra = 0;
for (int twos = 0; twos <= n - 2; ++twos) {
if (twos != 0) {
sum_other_two += two[ord2[ptr]];
if (is_under(ord2[ptr], X)) {
if (counted[X] == 0) {
sum_other_two += one[X];
counted[X] = 1;
extra++;
}
}
if (is_under(ord2[ptr], Y)) {
if (counted[Y] == 0) {
sum_other_two += one[Y];
counted[Y] = 1;
extra++;
}
}
counted[ord2[ptr]] = 1;
if (distX[ord2[ptr]] + distY[ord2[ptr]] == d) {
between -= one[ord2[ptr]];
cnt--;
}
ptr++;
}
for (int ones = 0; ones + twos + cnt <= n; ++ones) {
if (sum_other_two + between + get_sum_other_one(twos, ones) <= K) {
ans = max(ans, 2 * (twos + extra) + cnt + ones + (2 - extra));
}
}
}
return ans;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int t;
cin >> t;
while (t--) {
int N, X, Y, K;
cin >> N >> X >> Y >> K;
vector<int> U(N - 1, 0), V(N - 1, 0), W(N - 1, 0);
for (int i = 0; i < N - 1; ++i) {
cin >> U[i] >> V[i] >> W[i];
}
cout << max_score(N, X, Y, K, U, V, W) << "\n";
}
return 0;
}
/**
1
4 0 1 9
0 2 2
1 2 3
2 3 3
**/