Submission #1118730

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118730		Ntd123	Duathlon (APIO18_duathlon)	C++14	100 / 100	126 ms	30280 KiB

count_triplets

#include <bits/stdc++.h>
#define PB push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define bit(x, i) ((x >> i) & 1)
#define il (node * 2)
#define ir (il + 1)
#define mid (l + r)/2
#define maxn
#define ll long long
#define pii pair <int, int>
#define MOD 1000000007
#define Task "b2"
#define int long long
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int N = 200005;
int n, m, d, cnt = 0, com = 0, ans = 0;
int luu[N], low[N], s[N];
stack <int> st;
vector <int> a[N], tree[N];
void DFS(int x, int y){
    st.push(x);
    d++;
    luu[x] = low[x] = ++ cnt;
    for (int i: a[x]){
        if (i == y) continue;
        if (luu[i]) low[x] = min(low[x], luu[i]);
        else {
            DFS(i, x);
            low[x] = min(low[x], low[i]);
            if (luu[x] <= low[i]){
                com++;
                tree[x].PB(com);
                while (!tree[com].size() || tree[com].back() != i)
                    tree[com].PB(st.top()), st.pop();
            }
        }
    }
}
void DFS1(int x){
    s[x] = (x <= n);
    for (int i: tree[x]){
        DFS1(i);
        s[x] += s[i];
        if (i <= n) ans -= tree[x].size()*s[i]*(s[i]-1);
    }
    if (x    > n) ans -= tree[x].size()*(d-s[x])*(d-s[x]-1);
}
signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if(fopen(Task".inp", "r")) {
        freopen(Task".inp", "r", stdin);
        freopen(Task".out", "w", stdout);
    }
    cin >> n >> m;
    com = n;
    for (int i = 1; i <= m; i ++){
        int u, v;
        cin >> u >> v;
        a[u].PB(v);
        a[v].PB(u);
    }
    for (int i = 1; i <= n; i ++)
    if (!luu[i]){
        d=0;
        DFS(i, 0);
        ans += d*(d-1)*(d-2);
        DFS1(i);
    }
    cout << ans;
    cerr << "\nTime elapsed: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
    return 0;
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:57:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |         freopen(Task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
count_triplets.cpp:58:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   58 |         freopen(Task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• 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