#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
using namespace std;
const int maxn = 1e5 + 5;
int n, a[maxn], w[maxn];
vector <pair<int, long long>> g[maxn];
int used[maxn];
long long dp1[maxn], ben1[maxn];
long long dp2[maxn], ben2[maxn];
int sz[maxn];
long long answ;
void sizeCounter(int v, int p){
sz[v] = 1;
dp1[v] = dp2[v] = 0;
ben1[v] = ben2[v] = 0;
for (int i = 0; i < g[v].size(); i++){
int to = g[v][i].first;
if (to == p || used[to]) continue;
sizeCounter(to, v);
sz[v] += sz[to];
}
}
int center = 0;
void findCen(int v, int p){
int cnt = sz[v] / 2;
for (int i = 0; i < g[v].size(); i++){
int to = g[v][i].first;
if (to == p || used[to]) continue;
if (sz[to] >= cnt){
center = to;
findCen(to, v);
}
}
}
vector <long long> G;
void push_DP(int v, int p){
sz[v] = 1;
for (int i = 0; i < g[v].size(); i++){
int to = g[v][i].first;
int len = g[v][i].second;
if (to == p || used[to]) continue;
ben1[to] = ben1[v] + a[v] - len;
dp1[to] = dp1[v];
if (ben1[to] < 0){
dp1[to] -= ben1[to];
ben1[to] = 0;
}
int d = a[to] - len;
dp2[to] = dp2[v] + d;
ben2[to] = min(1ll * d, ben2[v] + d);
push_DP(to, v);
sz[v] += sz[to];
}
if (ben2[v] >= 0){
G.push_back(dp2[v]);
}
}
int findCenter(int v){
sizeCounter(v, -1);
center = v;
findCen(v, -1);
push_DP(center, -1);
return center;
}
vector <long long> P;
vector <int> ver;
void solve(int v, int p){
if (p != -1){
ver.push_back(v);
if (ben2[v] >= 0){
P.push_back(dp2[v]);
}
}
int idx = lower_bound(G.begin(), G.end(), dp1[v]) - G.begin();
answ += (int)G.size() - idx;
if (p == -1) answ--;
for (int i = 0; i < g[v].size(); i++){
int to = g[v][i].first;
if (to == p || used[to]) continue;
solve (to, v);
if (p == -1){
sort (P.begin(), P.end());
for (int j = 0; j < ver.size(); j++){
int u = ver[j];
int id = lower_bound(P.begin(), P.end(), dp1[u]) - P.begin();
answ -= (int)P.size() - id;
}
P.clear();
ver.clear();
}
}
}
void centroidDecomposition() {
queue <int> q;
q.push(1);
while (!q.empty()) {
int v = q.front();
q.pop();
v = findCenter(v);
sort(G.begin(), G.end());
solve(v, -1);
G.clear();
for (int i = 0; i < g[v].size(); i++){
int to = g[v][i].first;
if (used[to] || sz[to] == 1) continue;
q.push(to);
}
used[v] = 1;
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n;
for (int i = 1; i <= n; i++)
cin >> a[i];
for (int i = 0; i < n - 1; i++) {
int x, y, z;
cin >> x >> y >> z;
g[x].push_back({ y, z });
g[y].push_back({ x, z });
}
centroidDecomposition();
cout << answ << '\n';
return 0;
}
Compilation message
transport.cpp: In function 'void sizeCounter(int, int)':
transport.cpp:22:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < g[v].size(); i++){
~~^~~~~~~~~~~~~
transport.cpp: In function 'void findCen(int, int)':
transport.cpp:34:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < g[v].size(); i++){
~~^~~~~~~~~~~~~
transport.cpp: In function 'void push_DP(int, int)':
transport.cpp:48:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < g[v].size(); i++){
~~^~~~~~~~~~~~~
transport.cpp: In function 'void solve(int, int)':
transport.cpp:98:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < g[v].size(); i++){
~~^~~~~~~~~~~~~
transport.cpp:104:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int j = 0; j < ver.size(); j++){
~~^~~~~~~~~~~~
transport.cpp: In function 'void centroidDecomposition()':
transport.cpp:126:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < g[v].size(); i++){
~~^~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
50 ms |
3116 KB |
Output is correct |
| 2 |
Correct |
9 ms |
3136 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
883 ms |
3584 KB |
Output is correct |
| 2 |
Correct |
961 ms |
3772 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
1067 ms |
11168 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
1052 ms |
14060 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
1025 ms |
18292 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
1069 ms |
6112 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
89 ms |
7292 KB |
Output is correct |
| 2 |
Execution timed out |
1043 ms |
7216 KB |
Time limit exceeded |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
606 ms |
9128 KB |
Output is correct |
| 2 |
Correct |
251 ms |
8952 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
708 ms |
10800 KB |
Output is correct |
| 2 |
Correct |
407 ms |
10736 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
1043 ms |
13632 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
