Submission #567408

#	Time	Username	Problem	Language	Result	Execution time	Memory
567408		Jarif_Rahman	Duathlon (APIO18_duathlon)	C++17	10 / 100	1092 ms	26228 KiB

count_triplets

#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;

struct BIT{
    int n;
    vector<ll> sm;
    BIT(int _n){
        n = _n;
        sm.resize(n);
    }
    void add(int in, ll x){
        in++;
        while(in <= n) sm[in-1]+=x, in+=in&-in;
    }
    ll sum(int in){
        in++;
        ll s = 0;
        while(in >= 1) s+=sm[in-1], in-=in&-in;
        return s;
    }
    ll sum(int l, int r){
        return sum(r)-(l == 0? 0:sum(l-1));
    }
};

int n, m;
vector<vector<int>> v, tree, backedge;
vector<bool> bl;
vector<bool> marked;
vector<int> sz;
vector<int> pos;
vector<int> sth;

ll ans = 0;

void dfs_tree(int nd, int ss = -1){
    bl[nd] = 1;
    for(int x: v[nd]){
        if(!bl[x]){
            bl[x] = 1;
            tree[nd].pb(x);
            dfs_tree(x, nd);
        }
        else{
            if(x != ss) backedge[x].pb(nd);
        }
    }
}

void mark(int nd){
    marked[nd] = !marked[nd];
    for(int x: tree[nd]) mark(x);
}

int cnt = 0;

void pre_dfs(int nd){
    sz[nd] = 1;
    pos[nd] = cnt++;
    for(int x: tree[nd]) pre_dfs(x);
    for(int x: tree[nd]) sz[nd]+=sz[x];
}

int root;

BIT bit(0);

void dfs(int nd){
    for(int x: tree[nd]) dfs(x);
    for(int x: tree[nd]) sth[nd]+=sth[x];
    bool bkg = 0;
    for(int x: backedge[nd]) if(!marked[x]) bkg = 1;
    if(bkg){
        ll cur = sz[root]-sz[nd];
        cur-=bit.sum(pos[root], pos[root]+sz[root]-1)-bit.sum(pos[nd], pos[nd]+sz[nd]-1);
        cur*=2;
        cur*=sth[nd];
        sth[nd] = 0;
        ans+=cur;
        bit.add(pos[nd], 1);
    }
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> m;
    v.assign(n, {});

    for(int i = 0; i < m; i++){
        int a, b; cin >> a >> b; a--, b--;
        v[a].pb(b);
        v[b].pb(a);
    }

    marked.assign(n, 0);
    sz.resize(n);
    pos.resize(n);

    for(int i = 0; i < n; i++){
        tree.assign(n, {});
        backedge.assign(n, {});
        bl.assign(n, 0);
        sth.assign(n, 1);

        bit = BIT(n);

        dfs_tree(i);
        cnt = 0;
        pre_dfs(i);

        for(int x: tree[i]){
            ans+=ll(sz[i]-1-sz[x])*ll(sz[x]);
            root = x;
            mark(x);
            dfs(x);
            mark(x);
        }
    }

    cout << ans << "\n";
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 10 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10