Submission #445666

#	Time	Username	Problem	Language	Result	Execution time	Memory
445666		cpp219	Duathlon (APIO18_duathlon)	C++14	23 / 100	1124 ms	1048580 KiB

count_triplets

#pragma GCC optimization O2
#pragma GCC optimization "unroll-loop"
#pragma target ("avx2")

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define fs first
#define sc second
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 1e5 + 9;
const ll Log2 = 20;
const ll inf = 1e9 + 7;

vector<ll> g[N];
ll n,m,x,y,child[N],ans;

void DFS(ll u,ll p){
    child[u] = 1; ll now = 0;
    for (auto i : g[u]){
        if (i == p) continue;
        DFS(i,u); child[u] += child[i];
        now += child[i]*(child[i] - 1)/2;
    }
    ans += 2 * ((child[u] - 1) * (child[u] - 2)/2 - now);
}

void reDFS(ll u,ll p,ll sz){
    ans += 2 * (sz - child[u]) * (child[u] - 1);
    for (auto i : g[u]) if (i != p) reDFS(i,u,sz);
}

int main(){
    ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    #define task "test"
    if (fopen(task".INP","r")){
        freopen(task".INP","r",stdin);
        //freopen(task".OUT","w",stdout);
    }
    cin>>n>>m;
    while(m--){
        cin>>x>>y;
        g[x].push_back(y); g[y].push_back(x);
    }
    for (ll i = 1;i <= n;i++) if (!child[i]) DFS(i,0),reDFS(i,0,child[i]);
    //cout<<child[1]; return 0;
    cout<<ans;
}

Compilation message (stderr)

count_triplets.cpp:1: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    1 | #pragma GCC optimization O2
      | 
count_triplets.cpp:2: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    2 | #pragma GCC optimization "unroll-loop"
      | 
count_triplets.cpp:3: warning: ignoring '#pragma target ' [-Wunknown-pragmas]
    3 | #pragma target ("avx2")
      | 
count_triplets.cpp: In function 'int main()':
count_triplets.cpp:38:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   38 |         freopen(task".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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