Submission #710289

#	Time	Username	Problem	Language	Result	Execution time	Memory
710289		lam	Duathlon (APIO18_duathlon)	C++14	0 / 100	4 ms	2644 KiB

count_triplets

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int maxn = 1e5 + 10;
int n,m;
vector <int> adj[maxn];
int dp[maxn],dp2[maxn],s[maxn];
bool dau[maxn];
vector <int> root;
int ans = 0LL;
void dfs(int x, int p)
{
    dau[x] = 1;
    dp[x] = 0;
    for (int i:adj[x])
        if (i!=p)
    {
        dfs(i,x);
        dp[x] += dp[i]+1;
        int temp = (dp[i]+1);
        int temp2 = (n-temp-1);
        ans += temp*temp2;
    }
}

void dfs2(int x, int p, int val)
{
    dp2[x] = val;
    int temp = n-val-1;
    ans+=val*temp;
    val++;
    vector <int> pre,suf;
    for (int i:adj[x])
        if (i!=p)
    {
        pre.push_back(dp[i]+1);
        suf.push_back(dp[i]+1);
    }
    for (int i=1; i<pre.size(); i++) pre[i]+=pre[i-1];
    for (int i=suf.size()-2; i>=0; i--) suf[i]+=suf[i+1];
    int cnt=0;
    for (int i:adj[x])
        if (i!=p)
    {
        int val2 = val;
        if (cnt>0) val2 += pre[cnt-1];
        if (cnt<(int)suf.size()-1) val2+=suf[cnt+1];
        cnt++;
        dfs2(i,x,val2);
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
    freopen("dualthon.inp","r",stdin);
    freopen("dualthon.out","w",stdout);
    cin>>n>>m;
    for (int i=1; i<=m; i++)
    {
        int u,v; cin>>u>>v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    for (int i=1; i<=n; i++) if (!dau[i]) dfs(i,i), root.push_back(i);
    for (int i:root) dfs2(i,i,0);
    cout<<ans<<'\n';
}

Compilation message (stderr)

count_triplets.cpp: In function 'void dfs2(long long int, long long int, long long int)':
count_triplets.cpp:39:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |     for (int i=1; i<pre.size(); i++) pre[i]+=pre[i-1];
      |                   ~^~~~~~~~~~~
count_triplets.cpp: In function 'int main()':
count_triplets.cpp:57:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |     freopen("dualthon.inp","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
count_triplets.cpp:58:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   58 |     freopen("dualthon.out","w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• 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