#include<iostream>
#include<stack>
#include<map>
#include<vector>
#include<string>
#include<unordered_map>
#include <queue>
#include<cstring>
#include<float.h>
#include<limits.h>
#include <cassert>
#include<cmath>
#include<set>
#include<algorithm>
#include <iomanip>
#include<numeric> //gcd(a,b)
#include<bitset>
using namespace std;
#define ll long long
#define f first
#define endl "\n"
#define s second
#define pii pair<int,ll>
#define ppii pair<int,pii>
#define vi vector<int>
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define F(n) for(int i=0;i<n;i++)
#define lb lower_bound
#define ub upper_bound
using namespace std;
#define int long long
#define double long double
#define fastio ios::sync_with_stdio(false);cin.tie(NULL);
#pragma GCC optimize ("03,unroll-loops")
const int mod=98765431,mxn=1e5,lg=22,inf=1e18,minf=-1e9,Mxn=100000;
int val[mxn+10],n,sz[mxn+10],ans=0;
vector<pii>adj[mxn+10];
bool del[mxn+10];
struct node{
int mnpref,sum,mnsuf;
node operator+(node a)const{
node ans;
ans.mnpref=min(mnpref,sum+a.mnpref);
ans.mnsuf=min(a.mnsuf,a.sum+mnsuf);
ans.sum=sum+a.sum;
return ans;
}
};
node v[mxn+10];
void getsz(int cur,int p){
sz[cur]=1;
for(auto i:adj[cur])if(i.f!=p&&!del[i.f])getsz(i.f,cur),sz[cur]+=sz[i.f];
}
int getcen(int cur,int p,int mx){
for(auto i:adj[cur])if(i.f!=p&&!del[i.f]&&sz[i.f]>mx/2)return getcen(i.f,cur,mx);
return cur;
}
int cnt=0;
vector<int>deg[mxn+10];
int pos[mxn+10];
void solve(int cur,int p){
v[cur]=v[cur]+(node){val[cur],val[cur],val[cur]};
for(auto i:adj[cur]){
if(i.f!=p&&!del[i.f]){
v[i.f]=v[cur]+(node){-i.s,-i.s,-i.s};
solve(i.f,cur);
}
}
deg[cnt].pb(cur);
}
struct fen{
int fwk[mxn+10];
void update(int pos,int val){for(int i=pos;i<=n;i+=(i&-i))fwk[i]+=val;}
int qry(int pos){
int sum=0;
for(int i=pos;i>0;i-=(i&-i))sum+=fwk[i];
return sum;
}
}t;
bool cmp(pii a,pii b){return a.f<b.f;}
void decomp(int cur){
getsz(cur,-1);
int cen=getcen(cur,-1,sz[cur]);
v[cen].mnpref=v[cen].mnsuf=v[cen].sum=val[cen];
for(auto i:adj[cen]){
if(del[i.f])continue;
v[i.f]=v[cen]+(node){-i.s,-i.s,-i.s};
solve(i.f,cen);
cnt++;
}
vector<pii>a;
a.clear();
for(int i=0;i<cnt;i++)for(auto j:deg[i]){
if(v[j].mnpref>=0)ans++;
if(v[j].mnsuf>=0)ans++;
a.pb({-v[j].mnpref,j});
}
sort(all(a));
//if sum+mnpref-val[node]>=0 sum-val[node]>=-mnpref
for(int i=0;i<a.size();i++)pos[a[i].s]=i+1;
for(int i=0;i<cnt;i++){
for(auto j:deg[i])t.update(pos[j],1);
for(auto j:deg[i]){
if(v[j].mnsuf<0ll)continue;
// int it=ub(all(a),make_pair(v[j].sum-val[cen],inf),cmp)-a.begin()-1;
if(it<0)continue;
ans+=it+1-t.qry(it+1);
}
for(auto j:deg[i])t.update(pos[j],-1);
deg[i].clear();
}
del[cen]=true;
for(auto i:adj[cen])if(!del[i.f])decomp(i.f);
}
int32_t main(){
fastio
cin>>n;
for(int i=1;i<=n;i++)cin>>val[i];
for(int i=0;i<n-1;i++){
int a,b,w;cin>>a>>b>>w;
adj[a].pb({b,w});
adj[b].pb({a,w});
}
decomp(1);
cout<<ans;
}
Compilation message
transport.cpp: In function 'void decomp(long long int)':
transport.cpp:102:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
102 | for(int i=0;i<a.size();i++)pos[a[i].s]=i+1;
| ~^~~~~~~~~
transport.cpp:108:16: error: 'it' was not declared in this scope; did you mean 'i'?
108 | if(it<0)continue;
| ^~
| i
transport.cpp:109:18: error: 'it' was not declared in this scope; did you mean 'i'?
109 | ans+=it+1-t.qry(it+1);
| ^~
| i
