Submission #132996

#	Time	Username	Problem	Language	Result	Execution time	Memory
132996		ae04071	Duathlon (APIO18_duathlon)	C++11	0 / 100	113 ms	23952 KiB

count_triplets

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

int n,m,cut[100001],dfn[100001],low[100001],o,dn;
int bsz[200001];
vector<int> adj[100001],badj[200001];
stack<int> stk;

int ts;
void addEdge(int u,int v) {
    badj[u].push_back(v);
    badj[v].push_back(u);
}
void dfs(int cur,int p) {
    ts++;
    dfn[cur] = low[cur] = ++dn;
    stk.push(cur);
    for(auto &it:adj[cur]) if(it!=p) {
        if(dfn[it]) low[cur] = min(low[cur],dfn[it]);
        else {
            dfs(it,cur);
            low[cur] = min(low[cur],low[it]);
            if(low[it]>=dfn[cur]) {
                ++n;
                if(!cut[cur]) addEdge(n,cur);
                cut[cur] = 1;
                while(!stk.empty()) {
                    int v=stk.top();
                    bsz[n]++;
                    if(cut[v]) addEdge(n, v);
                    stk.pop();
                    if(v==it) break;
                }
                bsz[n]++;
            }
        }
    }
}

long long ans;
int sz[200001];
int cal_dfs(int cur,int p) {
    sz[cur] = bsz[cur];
    for(auto &it:badj[cur]) if(it!=p) sz[cur] += cal_dfs(it,cur);
    sz[cur] -= ((int)badj[cur].size() - (p>0) - (cur<=o));

    if(cur>o) {
        for(auto &it:badj[cur]) if(it!=p) ans += 1ll*(bsz[cur]-1)*sz[it]*(sz[it]-1);
        ans += 1ll*(bsz[cur]-1)*(ts-sz[cur]+1)*(ts-sz[cur]);
    }
    return sz[cur];
}

int main() {
    scanf("%d%d",&n,&m);
    for(int i=0,u,v;i<m;i++) {
        scanf("%d%d",&u,&v);
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    o = n;

    long long ret = 0;
    for(int i=1;i<=o;i++) if(!dfn[i]) {
        ts=0; ans=0;
        dfs(i,0);
        while(!stk.empty()) stk.pop();

        cal_dfs(i, 0);
        ret += 1ll*ts*(ts-1)*(ts-2) - ans;
    }
    printf("%lld\n",ret);
    
    return 0;
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:55:10: 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:57:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&u,&v);
         ~~~~~^~~~~~~~~~~~~~

• 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