Submission #51968

#	Time	Username	Problem	Language	Result	Execution time	Memory
51968		pzdba	Duathlon (APIO18_duathlon)	C++14	66 / 100	231 ms	51552 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
typedef long long LL;

pii edges[200005];
vector<pii> g[100005];
bool idx[200005];
int low[100005], vis[100005], p[100005];
LL sz[100005], T = 1;
void dfs1(int u, int p){
	vis[u] = low[u] = T++;
	for(int i=0;i<g[u].size();i++){
		int v = g[u][i].first;
		if(v == p) continue;
		if(vis[v]) low[u] = min(low[u], vis[v]);
		else{
			dfs1(v, u);
			low[u] = min(low[u], low[v]);
			if(low[v] > vis[u]) idx[g[u][i].second] = 1;
		}
	}
}

int root(int a){
	while(p[a] != a){
		p[a] = p[p[a]];
		a = p[a];
	}
	return a;
}
bool merge(int a, int b){
	a = root(a), b = root(b);
	if(a == b) return 0;
	sz[b] += sz[a];
	p[a] = b;
	return 1;
}

vector<int> scc[200005];
LL s[100005], sc[100005];
LL ans = 0;

void dfs2(int u, int p, int r){
	vis[u] = 1;
	s[u] += sz[u];
	sc[u] += (sz[u]-1)*(sz[u]-1);

	bool f = 0;
	for(int i=0;i<scc[u].size();i++){
		int cur = scc[u][i];

		LL s1 = 0, sc1 = 0;
		for(int j=0;j<g[cur].size();j++){
			int v = g[cur][j].first, edge = g[cur][j].second;
			int rv = root(v);
			if(!idx[edge]) continue;
			if(rv == p) continue;
			dfs2(rv, u, v);

			ans += sc[rv]*s[u]; // sc - f
			ans += s[rv]*sc[u]; // s - cf 

			ans += s[rv]*s1; // s - c - f

			s1 += s[rv];
			s[u] += s[rv];
			sc[u] += sc[rv];
		}

		for(int j=0;j<g[cur].size();j++){
			int v = g[cur][j].first, edge = g[cur][j].second;
			int rv = root(v);
			if(!idx[edge]) continue;
			if(rv == p) continue;

			if(cur == r) f = 1;

			sc[u] += s[rv]*sz[u];
		}
	}

	if(f){
		int cur = r;
		for(int j=0;j<g[cur].size();j++){
			int v = g[cur][j].first, edge = g[cur][j].second;
			int rv = root(v);
			if(!idx[edge]) continue;
			if(rv == p) continue;

			sc[u] -= s[rv]*sz[u];
			sc[u] += s[rv];
		}
	}
}

int main(){
	int n, m;
	scanf("%d%d", &n, &m);
	for(int i=0;i<m;i++){
		int a, b;
		scanf("%d%d", &a, &b);
		g[a].push_back(pii(b, i));
		g[b].push_back(pii(a, i));
		edges[i] = pii(a, b);
	}
	for(int i=1;i<=n;i++){
		if(vis[i]) continue;
		dfs1(i, 0);
	}
	for(int i=1;i<=n;i++) p[i] = i, sz[i] = 1;
	for(int i=1;i<=n;i++){
		for(int j=0;j<g[i].size();j++){
			int v = g[i][j].first, edge = g[i][j].second;
			if(!idx[edge]){
				merge(i, v);
			}
		}
	}
	for(int i=1;i<=n;i++){
		scc[root(i)].push_back(i);
	}
	memset(vis, 0, sizeof(vis));
	for(int i=1;i<=n;i++){
		if(vis[i]) continue;
	 	if(root(i) == i) dfs2(i, 0, 0);
	}
	ans *= 2;
	for(int i=1;i<=n;i++){
		if(root(i) == i){
			ans += (LL)sz[i]*(sz[i]-1)*(sz[i]-2);
		}
	}
	printf("%lld\n", ans);
}

Compilation message (stderr)

count_triplets.cpp: In function 'void dfs1(int, int)':
count_triplets.cpp:13:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<g[u].size();i++){
              ~^~~~~~~~~~~~
count_triplets.cpp: In function 'void dfs2(int, int, int)':
count_triplets.cpp:50:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<scc[u].size();i++){
              ~^~~~~~~~~~~~~~
count_triplets.cpp:54:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<g[cur].size();j++){
               ~^~~~~~~~~~~~~~
count_triplets.cpp:71:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<g[cur].size();j++){
               ~^~~~~~~~~~~~~~
count_triplets.cpp:53:14: warning: unused variable 'sc1' [-Wunused-variable]
   LL s1 = 0, sc1 = 0;
              ^~~
count_triplets.cpp:85:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<g[cur].size();j++){
               ~^~~~~~~~~~~~~~
count_triplets.cpp: In function 'int main()':
count_triplets.cpp:113:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<g[i].size();j++){
               ~^~~~~~~~~~~~
count_triplets.cpp:99:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~
count_triplets.cpp:102:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a, &b);
   ~~~~~^~~~~~~~~~~~~~~~

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