Submission #967873

#	Time	Username	Problem	Language	Result	Execution time	Memory
967873		socpite	Duathlon (APIO18_duathlon)	C++14	100 / 100	147 ms	32592 KiB

count_triplets

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

const int maxn = 2e5+5;

vector<int> g[maxn];
int sz[maxn], dp[maxn];
vector<int> blg[maxn];

int low[maxn], num[maxn];

int n, m, bcsz, old_n;
long long ans = 0;

int tdfs;
stack<int> stk;

void addedge(int a, int b){
    // cout << a << " " << b << endl;
    blg[a].push_back(b);
    blg[b].push_back(a);
}

void dfs(int x, int p){
    n++;
    stk.push(x);
    low[x] = num[x] = ++tdfs;
    for(auto v:g[x]){
        if(v == p)continue;
        if(num[v])low[x] = min(low[x], num[v]);
        else {
            dfs(v, x);
            low[x] = min(low[x], low[v]);
        }
    }
    if(p){
        if(low[x] == num[p]){
            bcsz++;
            while(stk.top() != x){
                addedge(stk.top(), bcsz);
                sz[bcsz]++;
                stk.pop();
            }
            addedge(x, bcsz);
            sz[bcsz]++;
            stk.pop();
            addedge(p, bcsz);
        }
        else if(low[x] == num[x]){
            stk.pop();
            bcsz++;
            sz[bcsz] = 1;
            addedge(x, bcsz);
            addedge(p, bcsz);

        }
    }
}

long long dfs2(int x, int p){
    dp[x] = (x <= old_n);
    long long re = 0;
    for(auto v: blg[x]){
        if(v == p)continue;
        re += dfs2(v, x);
        dp[x] += dp[v];
        if(x <= old_n){
            re += 1LL*dp[v]*(n - dp[v] - 1);
        }
        else {
            re += 1LL*(blg[x].size()-2)*dp[v]*(n-dp[v]);
        }
    }
    if(x <= old_n){
        re += 1LL*(n - dp[x])*(dp[x] - 1);
    }
    else {
        re += 1LL*(blg[x].size()-2)*(n - dp[x])*(dp[x]);
    }
    return re;
}

int main() {
    cin >> n >> m;
    while(m--){
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    bcsz = n;
    old_n = n;
    for(int i = 1; i <= old_n; i++){
        if(!num[i]){
            n = 0;
            dfs(i, 0);
            ans += dfs2(i, 0);
        }
    }
    cout << ans;
}

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