제출 #1047878

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1047878		vjudge1	Transport (COCI19_transport)	C++17	78 / 130	476 ms	25708 KiB

Main

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

#define int long long
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define FORD(i, a, b) for (int i = (b); i >= (a); i --)
#define REP(i, a) for (int i = 0; i < (a); ++i)
#define REPD(i, a) for (int i = (a) - 1; i >= 0; --i)

#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)


constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

/*
    Phu Trong from Nguyen Tat Thanh High School for gifted student
*/

template <class X, class Y>
    bool minimize(X &x, const Y &y){
        X eps = 1e-9;
        if (x > y + eps) {x = y; return 1;}
        return 0;
    }

template <class X, class Y>
    bool maximize(X &x, const Y &y){
        X eps = 1e-9;
        if (x + eps < y) {x = y; return 1;}
        return 0;
    }
#define MAX                 100005
#define N                   100000
int numNode;
int label[MAX];

struct Edge{
    int u, v, w;
    Edge(){}
    Edge(int _u, int _v, int _w): u(_u), v(_v), w(_w){}

    int other(int x){return (x ^ u ^ v);}
} edge[MAX];

vector<int> G[MAX];

int sz[MAX], del[MAX];

int reSubsize(int u, int p = -1){
    sz[u] = 1;
    for (int&i : G[u]){
        int v = edge[i].other(u);
        if(v ^ p){
            if(del[v]) continue;
            reSubsize(v, u);
            sz[u] += sz[v];
        }
    }
    return sz[u];
}

int findCentroid(int u, int p, int siz){
    for (int &i : G[u]){
        int v = edge[i].other(u);
        if(v ^ p){
            if (!del[v] && 2 * sz[v] > siz) return findCentroid(v, u, siz);
        }
    }
    return u;
}
int F[MAX];
vector<pair<int, int>> rback;
int low_bit(int p){
    return p & (-p);
}
void upd(int p, int val){
    if (val > 0) rback.emplace_back(p, -val);
    for (; p <= N; p += low_bit(p)) F[p] += val;
}

int query(int p){
    int res = 0;
    for (; p > 0; p -= low_bit(p)) res += F[p];
    return res;
}

void undo(void){
    while((int)rback.size()){
        int p, v; tie(p, v) = rback.back();
        upd(p, v);
        rback.pop_back();
    }
}

template<class T = vector<int>>
    void unique(T &v){
        sort(v.begin(), v.end());
        v.resize(unique(v.begin(), v.end()) - v.begin());
    }

vector<int> comp;
int find(int x){
    return lower_bound(comp.begin(), comp.end(), x) - comp.begin() + 1;
}

int up[MAX], down[MAX], pref[MAX];
int ans = 0;
void dfs_down(int u, int p, int sm){
    comp.push_back(-down[u]);
    if(down[u] >= 0) ++ans;
    for (int&i : G[u]){
        int v = edge[i].other(u);
        if(v ^ p){
            if (del[v]) continue;
            down[v] = min(sm - edge[i].w, down[u]);
            dfs_down(v, u, sm + label[v] - edge[i].w);
        }
    }
}

void dfs_up(int u, int p){
    comp.push_back(up[u]);
    comp.push_back(pref[u]);
    if(up[u] >= 0) ++ans;
    for (int &i : G[u]){
        int v = edge[i].other(u);
        if(v ^ p){
            if(del[v]) continue;
            pref[v] = pref[u] + label[v] - edge[i].w;
            up[v] = min(up[u] + label[v] - edge[i].w, label[v] - edge[i].w);
            dfs_up(v, u);
        }
    }
}

void dfs(int u, int p, bool add){
    if(add){
        int v = find(-down[u]);
        upd(v, 1);
    }
    else{
        int v = find(pref[u]);
        if(up[u] >= 0)
            ans += query(v);
    }

    for (int &i : G[u]){
        int v = edge[i].other(u);
        if(v ^ p){
            if(del[v]) continue;
            dfs(v, u, add);
        }
    }
}
void decompose(int root){
    int siz = reSubsize(root);
    root = findCentroid(root, root, siz);
    comp.clear();
    del[root] = true;
    for (int&i : G[root]) {
        int v = edge[i].other(root);
        if(del[v]) continue;
        down[v] = label[root] - edge[i].w;
        dfs_down(v, root, label[root] + label[v] - edge[i].w);

        pref[v] = label[v] - edge[i].w;
        up[v] = label[v] - edge[i].w;
        dfs_up(v, root);
    }
    sort(comp.begin(), comp.end());
    unique(comp);
    for (int &i : G[root]){
        int v = edge[i].other(root);
        if(del[v]) continue;
        dfs(v, root, 0);
        dfs(v, root, 1);
    }
    undo();
    reverse(G[root].begin(), G[root].end());

    for (int &i : G[root]){
        int v = edge[i].other(root);
        if(del[v]) continue;
        dfs(v, root, 0);
        dfs(v, root, 1);
    }
    undo();
    for (int&i : G[root]){
        int v = edge[i].other(root);
        if(del[v]) continue;
        decompose(v);
    }
}
void process(void){
    cin >> numNode;
    for (int i = 1; i <= numNode; ++i) cin >> label[i];
    for (int i = 1; i < numNode; ++i) {
        cin >> edge[i].u >> edge[i].v >> edge[i].w;
        G[edge[i].u].emplace_back(i);
        G[edge[i].v].emplace_back(i);
    }

    decompose(1);
    cout << ans;
}
signed main(){
    #define name "Whisper"
    cin.tie(nullptr) -> sync_with_stdio(false);
    //freopen(name".inp", "r", stdin);
    //freopen(name".out", "w", stdout);
    process();
    return (0 ^ 0);
}

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