671D - Roads in Yusland - CodeForces Solution

#include<bits/stdc++.h>
#define fi first
#define se second
#define endl "\n"
#define ii pair<int, int>
using namespace std;

const int N = 3e5 + 10;
int st[N], ed[N];
vector<pair<int, long long> > fix[N];
vector<int> adj[N], cancel[N];
long long T[N << 2], lazy[N << 2];
int n, m, cnt;

void push(int s, int l, int r) {
    if (!lazy[s]) return;
    T[s] += lazy[s];
    if (l != r) {
        lazy[s << 1] += lazy[s];
        lazy[s << 1 | 1] += lazy[s];
    }
    lazy[s] = 0;
}

void up(int s, int l, int r, int from, int to, long long val) {
    push(s, l, r);
    if (l > to || r < from) return;
    if (from <= l && r <= to) {
        lazy[s] += val;
        push(s, l, r);
        return;
    }
    int mid = l + r >> 1;
    up(s << 1, l, mid, from, to, val);
    up(s << 1 | 1, mid + 1, r, from, to, val);
    T[s] = min(T[s << 1], T[s << 1 | 1]);
}

long long get(int s, int l, int r, int from, int to) {
    push(s, l, r);
    if (l > to || r < from) return 1e15;
    if (from <= l && r <= to) return T[s];
    int mid = l + r >> 1;
    return min(get(s << 1, l, mid, from, to), get(s << 1 | 1, mid + 1, r, from, to));
}

void dfs(int u, int p = 0) {
    st[u] = 1e9;

    long long sum = 0;

    for(int &v : adj[u]) if (v != p) {
        dfs(v, u);
        st[u] = min(st[u], st[v]);
        sum += get(1, 1, m, st[v], ed[v]);
        if (sum >= 1e18) {
            cout << -1;
            exit(0);
        }
    }

    for(int &v : adj[u]) if (v != p) {
        long long ex = get(1, 1, m, st[v], ed[v]);
        up(1, 1, m, st[v], ed[v], sum - ex);
    }

    for(auto &[highest, cost] : fix[u]) {
        ++cnt; if (st[u] == 1e9) st[u] = cnt;

        cancel[highest].push_back(cnt);

        up(1, 1, m, cnt, cnt, cost + sum);
    }

    ed[u] = cnt;

    if (u == 1) return;

    for(auto &idx : cancel[u]) up(1, 1, m, idx, idx, 1e15);

}

int main() {
    #define task ""
    cin.tie(0) -> sync_with_stdio(0);
    if (fopen ("task.inp", "r")) {
        freopen ("task.inp", "r", stdin);
        freopen ("task.out", "w", stdout);
    }
    if (fopen (task".inp", "r")) {
        freopen (task".inp", "r", stdin);
        freopen (task".out", "w", stdout);
    }

    cin >> n >> m;

    if (n == 1) return cout << 0, 0;

    for(int i = 1; i < n; i++) {
        int x, y; cin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }

    for(int i = 1; i <= m; i++) {
        int u, v, c; cin >> u >> v >> c;
        fix[u].emplace_back(v, c);
    }


    dfs(1, 0);

    long long ans = get(1, 1, m, st[1], ed[1]);
    if (ans >= 1e15) ans = -1;
    cout << ans;
}