Submission #837786

#	Time	Username	Problem	Language	Result	Execution time	Memory
837786		jasmin	Dynamic Diameter (CEOI19_diameter)	C++17	11 / 100	5067 ms	269492 KiB

diameter

#include<bits/stdc++.h>
using namespace std;
#define int long long

const int INF=LLONG_MAX;
const int L=25;

struct segtree{ //lazy maximum segtree with add updates

    vector<int> tree;
    vector<int> lazy;

    segtree(int n){
        tree.assign(n*4, 0);
        lazy.assign(n*4, 0);
    }

    int update_node(int v, int add){
        tree[v] += add;
        lazy[v] += add;

        return tree[v];
    }

    void propagate(int l, int r, int v){
        if(lazy[v]==0) return;

        update_node(v*2+1, lazy[v]);
        update_node(v*2+2, lazy[v]);
        lazy[v]=0;
    }

    int update(int l, int r, int v, int ql, int qr, int add){
        if(qr<=l || r<=ql) return tree[v];
        if(ql<=l && r<=qr){
            return update_node(v, add);
        }
        propagate(l, r, v);
        int m=l+(r-l)/2;
        return tree[v] = max(update(l, m, v*2+1, ql, qr, add), update(m, r, v*2+2, ql, qr, add));
    }

    int query(int l, int r, int v, int ql, int qr){
        if(qr<=l || r<=ql) return 0;
        if(ql<=l && r<=qr){
            return tree[v];
        }
        int m=l+(r-l)/2;
        return max(query(l, m, v*2+1, ql, qr), query(m, r, v*2+2, ql, qr));
    }
};

struct segtree2{
    vector<int> tree;

    void init(int n){
        tree.assign(n*4, 0);
    }

    int update(int l, int r, int v, int x, int val){
        if(x<l || r<=x) return tree[v];
        if(l+1==r){
            return tree[v]=val;
        }
        int m=l+(r-l)/2;
        return tree[v] = max(update(l, m, v*2+1, x, val), update(m, r, v*2+2, x, val));
    }

    int query(){
        return tree[0];
    }
};

struct tree{
    int n;
    vector<pair<int,int> > edge;
    vector<vector<pair<int,int> > >adi;

    segtree2 segans;

    vector<int> level;
    vector<int> pc; //parent centroid

    vector<int> subtreesize;

    vector<int> curind;
    vector<set<pair<int, int> > >children;
    vector<set<pair<int, int> > >paths;

    vector<vector<int> > preind;
    vector<vector<int> > ssize;
    vector<vector<int> > paredge;
    vector<segtree> seg;

    tree(int ninput){
        n = ninput;
        edge.assign(n-1, {-1, -1});
        adi.assign(n, {});

        segans.init(n);

        level.assign(n, INF);
        pc.assign(n, -1);

        subtreesize.assign(n, 0);

        curind.assign(L, 0);
        children.assign(n, {});
        paths.assign(n, {});

        preind.assign(L, vector<int>(n, 0));
        ssize.assign(L, vector<int> (n, 0));
        paredge.assign(L, vector<int> (n, 0));
        seg.assign(L, segtree(n));
    }

    //centroids
    int dfs(int v, int p, int lev){ //precomputes the subtreesizes
 
        subtreesize[v] = 1;
        for(auto [u, d]: adi[v]){
            if(u==p || level[u]<lev) continue;

            subtreesize[v] += dfs(u, v, lev);
        }

        return subtreesize[v];
    }

    int centroiddfs(int v, int lev, int size){ //finds a centroid in a connected graph

        for(auto [u, d]: adi[v]){
            if(level[u] < lev) continue;

            if(subtreesize[u] > size/2){

                subtreesize[v] = size - subtreesize[u];
                return centroiddfs(u, lev, size);
            }
        }

        return v;
    }

    void find_centroids(int v, int lev, int centroidp){ //finds all centroids recursively
        int size = dfs(v, -1, lev);

        int centroid = centroiddfs(v, lev, size);
        level[centroid] = lev;
        pc[centroid]= centroidp;

        //compute all values for this component
        distancedfs(centroid, -1, 0, lev);
        
        for(auto [u, d]: adi[centroid]){
            if(level[u] < lev) continue;

            children[centroid].insert({preind[lev][u], u});
            int p = seg[lev].query(0, n, 0, preind[lev][u], preind[lev][u] + ssize[lev][u]);
            paths[centroid].insert({p, u});
        }
        paths[centroid].insert({0, -1});
        paths[centroid].insert({0, -2});

        int diameter = (*prev(paths[centroid].end())).first;
        diameter += (*prev(prev(paths[centroid].end()))).first;
    
        segans.update(0, n, 0, centroid, diameter);

        //find next centroids
        for(auto [u, d]: adi[centroid]){
            if(level[u] < lev) continue;

            find_centroids(u, lev+1, centroid);
        }
    }

    int distancedfs(int v, int p, int dist, int lev){

        preind[lev][v] = curind[lev];
        curind[lev] ++;

        seg[lev].update(0, n, 0, preind[lev][v], preind[lev][v]+1, dist);

        int s=1;
        for(auto [u, d]: adi[v]){
            if(u==p || level[u] < lev) continue;

            paredge[lev][u] = d;
            s += distancedfs(u, v, dist+d, lev);
        }

        ssize[lev][v] = s;
        return s;
    }


    int update_edge(int a, int b, int val){

        int c; int lev;
        if(level[a] > level[b]){

            c=a;    
            lev = level[a];
        }
        else{

            c=b;
            lev = level[b];
        }
        c = pc[c];
        lev--;

        for(; lev>=0; lev--){

            if(preind[lev][b]<preind[lev][a]){ 

                swap(a, b);
            } //=> a is an ancestor of b


            // update c
            int x = (*prev(children[c].upper_bound({preind[lev][b], b}))).second;
            int oldp = seg[lev].query(0, n, 0, preind[lev][x], preind[lev][x]+ssize[lev][x]);
            paths[c].erase({oldp, x});

            int add = val- paredge[lev][b];
            paredge[lev][b] = val;
            seg[lev].update(0, n, 0, preind[lev][b], preind[lev][b]+ssize[lev][b], add);

            int newp = seg[lev].query(0, n, 0, preind[lev][x], preind[lev][x] + ssize[lev][x]);
            paths[c].insert({newp, x});


            int diameterc = (*prev(paths[c].end())).first;
            diameterc += (*prev(prev(paths[c].end()))).first;
            
            segans.update(0, n, 0, c, diameterc);

            c = pc[c];
        }

        return segans.query();
    }
};

int solve(int n, vector<int>& v, vector<int>& u, vector<int>& w){
    tree g(n);

    for(int i=0; i<n-1; i++){
        int a=v[i];
        int b=u[i];
        int c=w[i];

        g.edge[i]={a, b};
        g.adi[a].push_back({b, c});
        g.adi[b].push_back({a, c});
    }

    g.find_centroids(0, 0, -1);

    int ans=g.segans.query();
    return ans;
}

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n, q, maxw;
    cin >> n >> q >> maxw;

    vector<int> v(n-1);
    vector<int> u(n-1);
    vector<int> w(n-1);
    for(int i=0; i<n-1; i++){
        cin >> v[i] >> u[i] >> w[i];
        v[i]--;
        u[i]--;
    }

    int last=0;
    for(int i=0; i<q; i++){

        int di, wi;
        cin >> di >> wi;

        int d = (di + last) % (n-1);
        int weight = (wi + last) % maxw;

        w[d] = weight;

        int ans= solve(n, v, u, w);
        cout << ans << "\n";
        last = ans;
    }

    /*tree g(n);

    for(int i=0; i<n-1; i++){
        int a, b, c;
        cin >> a >> b >> c;
        a--; b--;

        g.edge[i]={a, b};
        g.adi[a].push_back({b, c});
        g.adi[b].push_back({a, c});
    }

    g.find_centroids(0, 0, -1);

    int last=0;
    for(int i=0; i<q; i++){

        int di, wi;
        cin >> di >> wi;

        int d = (di + last) % (n-1);
        int w = (wi + last) % maxw;

        auto [a, b] = g.edge[d];


        int ans=g.update_edge(a, b, w);
        cout << ans << "\n";
        
        last = ans;
    }*/
}

• Subtask 1: 11 / 11
• Subtask 2: 0 / 13
• Subtask 3: 0 / 7
• Subtask 4: 0 / 18
• Subtask 5: 0 / 24
• Subtask 6: 0 / 27