// Om Namah Shivaya
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a, b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a, b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
/*
*/
const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
vector<pll> adj[N];
vector<ll> a(N);
vector<bool> rem(N);
vector<ll> subsiz(N);
ll dfs1(ll u, ll p) {
subsiz[u] = 1;
for (auto [v, w] : adj[u]) {
if (v == p or rem[v]) conts;
subsiz[u] += dfs1(v, u);
}
return subsiz[u];
}
ll dfs2(ll u, ll p, ll nodes) {
for (auto [v, w] : adj[u]) {
if (v == p or rem[v]) conts;
if (subsiz[v] > nodes / 2) {
return dfs2(v, u, nodes);
}
}
return u;
}
vector<ll> sumup(N), mnprefup(N);
vector<array<ll, 3>> here[N];
ll curr_centroid;
vector<ll> sub_roots;
void dfs3(ll u, ll p, ll uu, ll sumdown, ll mnprefdown) {
here[curr_centroid].pb({sumup[u], mnprefup[u], mnprefdown});
if (uu != -1) {
here[uu].pb({sumup[u], mnprefup[u], mnprefdown});
}
for (auto [v, w] : adj[u]) {
if (v == p or rem[v]) conts;
sumup[v] = a[v] - w + sumup[u];
mnprefup[v] = min(a[v] - w, a[v] - w + mnprefup[u]);
ll uu2 = uu;
if (uu == -1) {
uu2 = v;
sub_roots.pb(v);
}
dfs3(v, u, uu2, sumdown + a[u] - w, min(mnprefdown, sumdown + a[u] - w));
}
}
ll get(vector<array<ll, 3>> v) {
vector<ll> vals;
for (auto [sum, mnprefup, mnprefdown] : v) {
vals.pb(mnprefdown);
}
sort(all(vals));
ll res = 0;
for (auto [sum, mnprefup, mnprefdown] : v) {
if (mnprefup < 0) conts;
ll cnt = vals.end() - lower_bound(all(vals), -sum);
if (mnprefdown >= -sum) {
cnt--;
}
res += cnt;
}
return res;
}
ll ans = 0;
void build(ll u, ll p) {
ll nodes = dfs1(u, -1);
ll centroid = dfs2(u, -1, nodes);
rem[centroid] = 1;
sumup[centroid] = 0;
mnprefup[centroid] = 0;
curr_centroid = centroid;
sub_roots.clear();
dfs3(centroid, -1, -1, 0, 0);
trav(v, sub_roots) {
ans -= get(here[v]);
here[v].clear();
here[v].shrink_to_fit();
}
ans += get(here[centroid]);
here[centroid].clear();
here[centroid].shrink_to_fit();
for (auto [v, w] : adj[centroid]) {
if (rem[v]) conts;
build(v, centroid);
}
}
void solve(int test_case)
{
ll n; cin >> n;
rep1(i, n) cin >> a[i];
rep1(i, n - 1) {
ll u, v, w; cin >> u >> v >> w;
adj[u].pb({v, w}), adj[v].pb({u, w});
}
build(1, -1);
cout << ans << endl;
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
10 ms |
8532 KB |
Output is correct |
| 2 |
Correct |
10 ms |
8660 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
14 ms |
8916 KB |
Output is correct |
| 2 |
Correct |
14 ms |
9172 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
104 ms |
16280 KB |
Output is correct |
| 2 |
Correct |
97 ms |
15608 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
145 ms |
19084 KB |
Output is correct |
| 2 |
Correct |
148 ms |
21308 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
198 ms |
23564 KB |
Output is correct |
| 2 |
Correct |
242 ms |
26580 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
69 ms |
11360 KB |
Output is correct |
| 2 |
Correct |
39 ms |
10988 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
74 ms |
13548 KB |
Output is correct |
| 2 |
Correct |
110 ms |
13268 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
153 ms |
15144 KB |
Output is correct |
| 2 |
Correct |
147 ms |
15444 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
224 ms |
17792 KB |
Output is correct |
| 2 |
Correct |
202 ms |
17888 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
275 ms |
20828 KB |
Output is correct |
| 2 |
Correct |
249 ms |
19748 KB |
Output is correct |
