#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define pb push_back
#define rc (i<<1)|1
#define lc (i<<1)
#define s second
#define f first
#define el "\n"
#define int long long
typedef long long ll;
const int MM=1e5+5, MOD=1e9+7, LOG=19;
int N, sz[MM], bk[MM], g[MM]; ll ans;
vector<pair<int,int>> adj[MM];
vector<ll> vdw, vup;
void dfs_up(int u, int pa, ll gc, ll lo) {
if(lo>=0) ++ans, vup.pb(lo);
for(auto &e:adj[u]) if(e.f!=pa&&!bk[e.f]) {
dfs_up(e.f, u, gc+g[e.f]-e.s, min(lo+g[e.f]-e.s, g[e.f]-e.s));
}
}
void dfs_dw(int u, int pa, ll gc, ll hi) {
if(hi<=0) ++ans;
vdw.pb(hi);
for(auto &e:adj[u]) if(e.f!=pa&&!bk[e.f]) {
dfs_dw(e.f, u, gc-g[u]+e.s, max(hi, gc-g[e.f]+e.s));
}
}
inline void solve(int rt) {
vector<ll> gdw, gup;
for(auto &e:adj[rt]) if(!bk[e.f]) {
vdw.clear(); vup.clear();
dfs_dw(e.f, rt, e.s-g[rt], e.s-g[rt]);
dfs_up(e.f, rt, g[e.f]-e.s, g[e.f]-e.s);
sort(begin(vup), end(vup));
sort(begin(vdw), end(vdw));
for(ll &x:vdw) gdw.pb(x);
for(ll &x:vup) gup.pb(x);
for(int i=0, j=0, sz=vup.size(); i<vdw.size(); i++) {
while(j<sz&&vup[j]<vdw[i]) ++j;
ans-=sz-j;
}
}
sort(begin(gup), end(gup));
sort(begin(gdw), end(gdw));
for(int i=0, j=0, sz=gup.size(); i<gdw.size(); i++) {
while(j<sz&&gup[j]<gdw[i]) ++j;
ans+=sz-j;
}
}
void gsz(int u, int pa) {
sz[u]=1;
for(auto &e:adj[u]) if(e.f!=pa&&!bk[e.f]) {
gsz(e.f, u); sz[u]+=sz[e.f];
}
}
int crt(int u, int th, int pa) {
for(auto &e:adj[u]) if(e.f!=pa&&!bk[e.f]) {
if(sz[e.f]>th) return crt(e.f, th, u); }
return u;
}
void rec(int u, int nd) {
gsz(u, 0);
int ct=crt(u, nd/2, 0);
bk[ct]=1;
if(nd==1) return;
solve(ct); gsz(ct, 0);
for(auto &e:adj[ct]) if(!bk[e.f]) rec(e.f, sz[e.f]);
}
int32_t main() {
cin.tie(nullptr)->sync_with_stdio(false);
cin>>N;
for(int i=1; i<=N; i++) cin>>g[i];
for(int i=1; i<N; i++) {
int u, v, w; cin>>u>>v>>w;
adj[u].pb({v,w});
adj[v].pb({u,w});
}
rec(1, N);
cout<<ans<<el;
}
// MM
Compilation message
transport.cpp: In function 'void solve(long long int)':
transport.cpp:44:43: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
44 | for(int i=0, j=0, sz=vup.size(); i<vdw.size(); i++) {
| ~^~~~~~~~~~~
transport.cpp:51:39: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
51 | for(int i=0, j=0, sz=gup.size(); i<gdw.size(); i++) {
| ~^~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
8 ms |
2892 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
11 ms |
3252 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
89 ms |
9064 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
111 ms |
11364 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
201 ms |
14688 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
79 ms |
5188 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
62 ms |
6724 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
184 ms |
7916 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
266 ms |
9900 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
323 ms |
12136 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
