Submission #924272

#	Time	Username	Problem	Language	Result	Execution time	Memory
924272		codefox	Duathlon (APIO18_duathlon)	C++14	0 / 100	1 ms	348 KiB

count_triplets

#include<bits/stdc++.h>
    
using namespace std;
    
#define ll long long
    
vector<vector<int>> graph;
vector<vector<int>> cgraph;
vector<int> comp;
vector<int> art;
vector<int> low;
vector<int> num;
vector<int> vis;
stack<int> s;
int c = 0;
int d = 0;
int root = 0;
int sub = 0;
vector<ll> compsize;
ll sol = 0;
int n, m;
    
void dfs(int i, int p)
{
    num[i] = low[i] = ++c;
    s.push(i);
    for (int ele:graph[i])
    {
        if (ele == p) continue;
        if (!num[ele]) 
        {
            if (i == root) sub++;
            dfs(ele, i);
            if (low[ele]>=num[i]) art[i] = 1;
            if (low[ele]==num[i])
            {
                while(s.top() != i)
                {
                    comp[s.top()] = d;
                    compsize[d]++;
                    s.pop();
                }
                comp[i] = d;
                compsize[d]++;
                s.pop();
                d++;
            }
        }
        low[i] = min(low[i], low[ele]);
    }
    if (num[i]==low[i] && comp[i]==-1)
    {
        art[i] = 1;
        while (s.top() != i)
        {
            comp[s.top()] = d;
            compsize[d]++;
            s.pop();
        }
        comp[i] = d;
        compsize[d]++;
        s.pop();
        d++;
    }
}
    
int dfs2(int i)
{
    vis[i] = 1;
    ll ss = 0;
    vector<int> cs;
    vector<int> v;
    for (int ele:cgraph[i])
    {
        if (!vis[ele]) 
        {
            if (ele < n) cs.push_back(compsize[ele]-1);
            int h  = dfs2(ele);
            if (ele < n) h--;
            v.push_back(h);
            ss += v.back();
        }
    }
    if (i >= n)
    {
        for (ll ele:cs)
        {
            if (ele) sol += (ele-1)*(ele-2);
        }
        for (ll ele:v)
        {
            sol += ele*(sub-ele-1);
        }
    }
    else
    {
        sol += (compsize[i]-1)*(compsize[i]-2)*compsize[i];
        for (ll ele:v)
        {
            sol += ele*(sub-ele-1)*compsize[i];
        }
    }
    return ss+1;
}
    
int main()
{
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    
    cin >> n >> m;
    graph.assign(n, vector<int>());
    cgraph.assign(2*n, vector<int>());
    compsize.assign(n, 0);
    low.assign(n, 0);
    num.assign(n, 0);
    comp.assign(n, -1);
    art.assign(n, 0);
    vis.assign(2*n, 0);
    
    for (int i =0; i < m; i++)
    {
        int a, b;
        cin >> a >> b;
        a--; b--;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    vector<int> subtree(n, 0);
    
    for (int i = 0; i < n; i++)
    {
        if (!num[i]) 
        {
            root = i;
            sub = 0;
            c = 0;
            dfs(i, -1);
            subtree[i] = c;
            if (sub==1) art[i] = 0;
        }
    }
    
    d = n;
    for (int i = 0; i <n; i++)
    {
        if (art[i])
        {
            compsize[comp[i]]--;
            for (int ele:graph[i])
            {
                cgraph[d].push_back(comp[ele]);
                cgraph[comp[ele]].push_back(d);
            }
            comp[i] = d;
            d++;
        }
    }
    
    for (int i = 0; i < n; i++)
    {
        if (!vis[comp[i]])
        {
            sub = subtree[i];
            dfs2(comp[i]);
        }
    }
    cout << sol << "\n";
    
    return 0;
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:108:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  108 |     freopen("input.txt", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
count_triplets.cpp:109:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  109 |     freopen("output.txt", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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