Submission #62186

#	Time	Username	Problem	Language	Result	Execution time	Memory
62186		qkxwsm	Duathlon (APIO18_duathlon)	C++17	0 / 100	220 ms	38052 KiB

count_triplets

/*
PROG: source
LANG: C++11
    _____
  .'     '.
 /  0   0  \
|     ^     |
|  \     /  |
 \  '---'  /
  '._____.'
 */
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;

struct chash
{
    int operator()(int x) const
	{
		x ^= (x >> 20) ^ (x >> 12);
    	return x ^ (x >> 7) ^ (x >> 4);
	}
	int operator()(long long x) const
	{
		return x ^ (x >> 32);
	}
};

template<typename T> using orderedset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> using hashtable = gp_hash_table<T, T, chash>;

template<class T>
void readi(T &x)
{
	T input = 0;
	bool negative = false;
	char c = ' ';
	while (c < '-')
	{
		c = getchar();
	}
	if (c == '-')
	{
		negative = true;
		c = getchar();
	}
	while (c >= '0')
	{
		input = input * 10 + (c - '0');
		c = getchar();
	}
	if (negative)
	{
		input = -input;
	}
	x = input;
}
template<class T>
void printi(T output)
{
	if (output == 0)
	{
		putchar('0');
		return;
	}
	if (output < 0)
	{
		putchar('-');
		output = -output;
	}
	int aout[20];
	int ilen = 0;
	while(output)
	{
		aout[ilen] = ((output % 10));
		output /= 10;
		ilen++;
	}
	for (int i = ilen - 1; i >= 0; i--)
	{
		putchar(aout[i] + '0');
	}
	return;
}
template<class T>
void ckmin(T &a, T b)
{
	a = min(a, b);
}
template<class T>
void ckmax(T &a, T b)
{
	a = max(a, b);
}
template<class T>
T normalize(T x, T mod = 1000000007)
{
	return (((x % mod) + mod) % mod);
}
long long randomizell(long long mod)
{
	return ((1ll << 45) * rand() + (1ll << 30) * rand() + (1ll << 15) * rand() + rand()) % mod;
}
int randomize(int mod)
{
	return ((1ll << 15) * rand() + rand()) % mod;
}

#define y0 ___y0
#define y1 ___y1
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define debug(x) cerr << #x << " = " << x << endl;

const long double PI = 4.0 * atan(1.0);
const long double EPS = 1e-10;

#define MAGIC 347
#define SINF 10007
#define CO 1000007
#define INF 1000000007
#define BIG 1000000931
#define LARGE 1696969696967ll
#define GIANT 2564008813937411ll
#define LLINF 2696969696969696969ll
#define MAXN 100013

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pdd;

int N, M, T, K;
vector<int> edge[MAXN], edge1[MAXN];
int sz[MAXN];
vector<pii> bridge;
vector<pii> edges;
bool ap[MAXN];
vector<int> bcc[MAXN];
int id[MAXN], aid[MAXN];
int parent[MAXN];
int subtree[MAXN];
int disc[MAXN], low[MAXN];
bool seen[MAXN];
ll ans;

void dfs(int u, bool head = false)
{
    disc[u] = T;
    low[u] = T;
    seen[u] = true;
    T++;
    int children = 0;
    for (int v : edge[u])
    {
        if (v == parent[u])
        {
            continue;
        }
        if (seen[v])
        {
            ckmin(low[u], low[v]);
            continue;
        }
        children++;
        parent[v] = u;
        edges.PB({u, v});
        dfs(v);
        ckmin(low[u], low[v]);
        if (low[v] >= disc[u])
        {
            if (low[v] != disc[u])
            {
                bridge.PB({u, v});
            }
            if (!head)
            {
                ap[u] = true;
                while(edges.back() != MP(u, v))
                {
                    bcc[K].PB(edges.back().fi);
                    bcc[K].PB(edges.back().se);
                    edges.pop_back();
                }
                bcc[K].PB(edges.back().fi);
                bcc[K].PB(edges.back().se);
                edges.pop_back();
                K++;
            }
        }
        if (head)
        {
            if (children > 1)
            {
                ap[u] = true;
            }
            while(edges.back() != MP(u, v))
            {
                bcc[K].PB(edges.back().fi);
                bcc[K].PB(edges.back().se);
                edges.pop_back();
            }
            bcc[K].PB(edges.back().fi);
            bcc[K].PB(edges.back().se);
            edges.pop_back();
            K++;
        }
    }
}
void dfs1(int u)
{
    subtree[u] = sz[u];
    for (int v : edge1[u])
    {
        if (v == parent[u])
        {
            continue;
        }
        parent[v] = u;
        dfs1(v);
        subtree[u] += subtree[v];
    }
    return;
}

int32_t main()
{
	ios_base::sync_with_stdio(0);
	srand(time(0));
	//	cout << fixed << setprecision(10);
	//	cerr << fixed << setprecision(10);
	if (fopen("input.in", "r"))
	{
		freopen ("input.in", "r", stdin);
		freopen ("output.out", "w", stdout);
	}
    cin >> N >> M;
    for (int i = 0; i < M; i++)
    {
        int u, v;
        cin >> u >> v;
        u--; v--;
        edge[u].PB(v);
        edge[v].PB(u);
    }
    for (int i = 0; i < N; i++)
    {
        parent[i] = N;
    }
    dfs(0, 1);
    for (int i = 0; i < K; i++)
    {
        sort(bcc[i].begin(), bcc[i].end());
        bcc[i].erase(unique(bcc[i].begin(), bcc[i].end()), bcc[i].end());
        // cerr << "bcc # " << i << ":";
        for (int u : bcc[i])
        {
            // cerr << ' ' << u;
            id[u] = i;
            if (!ap[u])
            {
                sz[i]++;
            }
        }
        // cerr << endl;
    }
    for (int i = 0; i < N; i++)
    {
        if (ap[i])
        {
            aid[i] = K;
            sz[K] = 1;
            K++;
        }
    }
    for (int i = 0; i < K; i++)
    {
        for (int u : bcc[i])
        {
            if (ap[u])
            {
                edge1[i].PB(aid[u]);
                edge1[aid[u]].PB(i);
            }
        }
    }
    // for (int i = 0; i < K; i++)
    // {
    //     for (int v : edge1[i])
    //     {
    //         cerr << i << "->" << v << endl;
    //     }
    //     cerr << "size " << i << " = " << sz[i] << endl;
    // }
    for (int i = 0; i < N; i++)
    {
        parent[i] = N;
    }
    dfs1(0);
    for (int i = 0; i < K; i++)
    {
        //three guys all from here:
        int up = N - subtree[i], mid = sz[i], lo = subtree[i] - sz[i];
        // cerr << up << ' ' << mid << ' ' << lo << endl;
        //choose mid from here:
        ll cur = 0;
        //UMM
        cur += up * mid * (mid - 1);
        //UML
        cur += up * mid * lo;
        //MMU
        cur += mid * (mid - 1) * up;
        //MMM
        cur += mid * (mid - 1) * (mid - 2);
        //MML
        cur += mid * (mid - 1) * lo;
        //LMM
        cur += lo * mid * (mid - 1);
        //LMU
        cur += lo * mid * up;
        for (int v : edge1[i])
        {
            cur += sz[v] * (sz[v] - 1);
        }
        // cerr << "mid " << i << ' ' << cur << endl;
        ans += cur;
    }
    cout << ans << '\n';
	//	cerr << "time elapsed = " << (clock() / (CLOCKS_PER_SEC / 1000)) << " ms" << endl;
	return 0;
}

Compilation message (stderr)

count_triplets.cpp: In function 'int32_t main()':
count_triplets.cpp:244:11: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   freopen ("input.in", "r", stdin);
   ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
count_triplets.cpp:245:11: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   freopen ("output.out", "w", stdout);
   ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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