Submission #693820

#TimeUsernameProblemLanguageResultExecution timeMemory
693820sunwukong123Transport (COCI19_transport)C++14
13 / 130
1093 ms41544 KiB
#include <bits/stdc++.h> using namespace std; #define int long long #define FOR(i,s,e) for(int i = s; i <= (int)e; ++i) #define DEC(i,s,e) for(int i = s; i >= (int)e; --i) #define IAMSPEED ios_base::sync_with_stdio(false); cin.tie(0); #ifdef LOCAL #define db(x) cerr << #x << "=" << x << "\n" #define db2(x, y) cerr << #x << "=" << x << " , " << #y << "=" << y << "\n" #define db3(a,b,c) cerr<<#a<<"="<<a<<","<<#b<<"="<<b<<","<<#c<<"="<<c<<"\n" #define dbv(v) cerr << #v << ":"; for (auto ite : v) cerr << ite << ' '; cerr <<"\n" #define dbvp(v) cerr << #v << ":"; for (auto ite : v) cerr << "{" << ite.f << ',' << ite.s << "} "; cerr << "\n" #define dba(a,ss,ee) cerr << #a << ":"; FOR(ite,ss,ee) cerr << a[ite] << ' '; cerr << "\n" #define reach cerr << "LINE: " << __LINE__ << "\n"; #else #define reach #define db(x) #define db2(x,y) #define db3(a,b,c) #define dbv(v) #define dbvp(v) #define dba(a,ss,ee) #endif mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); #define pb push_back #define eb emplace_back #define all(x) (x).begin(), (x).end() #define f first #define s second #define g0(x) get<0>(x) #define g1(x) get<1>(x) #define g2(x) get<2>(x) #define g3(x) get<3>(x) typedef pair <int, int> pi; typedef tuple<int,int,int> ti3; typedef tuple<int,int,int,int> ti4; int rand(int a, int b) { return a + rng() % (b-a+1); } const int MOD = 1e9 + 7; const int inf = (int)1e9 + 500; const long long oo = (long long)1e18 + 500; template <typename T> bool chmax(T& a, const T b) { return a<b ? a = b, 1 : 0; } template <typename T> bool chmin(T& a, const T b) { return a>b ? a = b, 1 : 0; } const int MAXN = 100005; int A[MAXN]; int n; vector<pi> adj[MAXN]; int lvl[MAXN]; int sz[MAXN]; int par[MAXN]; int dist[MAXN][20]; // dist from the centroid of this level int dfs_sz(int x, int p) { if(sz[x])return sz[x]; sz[x] = 1; for(auto v:adj[x]) { if(v.f == p || lvl[v.f] != -1)continue; sz[x]+=dfs_sz(v.f,x); } return sz[x]; } int dfs2(int x, int p, int S) { //trying to find the centroid for(auto v:adj[x]){ if(v.f == p || lvl[v.f] != -1)continue; if(dfs_sz(v.f, x) > S/2)return dfs2(v.f,x,S); } return x; } namespace fw { map<int,int> fw; void update(int x, int nval) { ++x; for(;x<=oo;x+=x&-x){ fw[x]+=nval; } } int point(int x) { int t=0; for(;x;x-=x&-x){ t+=fw[x]; } return t; } int query(int x, int y) { ++x;++y; return point(y) - point(x-1); } } void dfs3(int x, int p, int l, int mx) { // do stuff for(auto v:adj[x]) { if(v.f == p || lvl[v.f] != -1)continue; dist[v.f][l] = dist[x][l] - v.s + A[v.f]; dfs3(v.f, x, l, max(mx, dist[v.f][l])); } // this is the start point if(dist[x][l] >= mx) { fw::update(dist[x][l], 1); } } int ans; void dfs4(int x, int p, int l, int mn){ for(auto v:adj[x]) { if(v.f == p || lvl[v.f] != -1)continue; dist[v.f][l] = dist[x][l] - v.s + A[v.f]; dfs4(v.f,x,l,min(mn, dist[v.f][l] - A[v.f])); } //dbvp(fw::fw); db2(x,mn); ans += fw::query(abs(mn), oo); } void build(int x, int p, int l) { int s=dfs_sz(x,p); int cent = dfs2(x,p,s); if(p == -1) p = cent; fw::update(A[cent], 1); for(auto v:adj[cent]){ if(v.f == p || lvl[v.f] != -1)continue; dist[v.f][l] = -v.s+A[v.f]; dfs4(v.f,cent,l,min(0ll, -v.s)); // consider this to be the end point dist[v.f][l]=A[cent] - v.s + A[v.f]; dfs3(v.f,cent,l,max(A[cent],dist[v.f][l])); // consider this to be the start point } fw::fw.clear(); reverse(all(adj[cent])); for(auto v:adj[cent]){ if(v.f == p || lvl[v.f] != -1)continue; //what if this child is the end point? dist[v.f][l] = A[cent]-v.s+A[v.f]; dfs4(v.f,cent,l,min(0ll, A[cent]-v.s)); // query with these ending nodes dist[v.f][l]= -v.s + A[v.f]; dfs3(v.f,cent,l,max(0ll,dist[v.f][l])); // add all potential starting nodes } ans += fw::query(0,oo); fw::fw.clear(); par[cent] = p; lvl[cent] = l; for(auto v:adj[cent]) { if(lvl[v.f] != -1)continue; build(v.f, cent, l+1); } } int32_t main() { IAMSPEED memset(lvl,-1,sizeof lvl); cin >> n; FOR(i,1,n) cin >> A[i]; FOR(i,1,n-1) { int a,b,c; cin >> a >> b >> c; adj[a].pb({b,c}); adj[b].pb({a,c}); } build(1,-1,0); cout << ans; return (0-0) ; }
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