Submission #280064

#	Time	Username	Problem	Language	Result	Execution time	Memory
280064		oolimry	Duathlon (APIO18_duathlon)	C++14	100 / 100	407 ms	58808 KiB

count_triplets

#include <bits/stdc++.h>

using namespace std;
int n, m;
typedef vector<int> vi;
typedef pair<int,int> ii;
struct node{
    int depth = -1;
    int low;
    int parent;
    bool vis = false;
    bool isArti = false;
    vi adj;
};
vector<unordered_set<int> > biconnected;
stack<int> s; ///this is only needed for biconnected components
///note: this will ignore single nodes with no edges
static node g[200005];
int rootChildren = 0;
void dfs(int u){
    if(g[u].depth == -1) g[u].depth = g[g[u].parent].depth + 1;
    g[u].low = g[u].depth;
    g[u].vis = true;
    for(int i = 0;i < g[u].adj.size();i++){
        int v = g[u].adj[i];
        if(!g[v].vis){
            g[v].parent = u;
            if(g[u].depth == 0) rootChildren++;
            s.push(u); ///s traces the path of tree traversal
            dfs(v);
            g[u].low = min(g[u].low,g[v].low);

            if(g[v].low >= g[u].depth){
                g[u].isArti = true;
                g[u].low = min(g[u].low,g[v].low);
                unordered_set<int> newSet;
                int nn;
                biconnected.push_back(newSet); ///create new biconnected component
                do{
                    assert(!s.empty());
                    nn = s.top();
                    s.pop();
                    biconnected.back().insert(nn);
                }while(nn != u);
            }
        }
        else if(v != g[u].parent){
            g[u].low = min(g[u].low,g[v].depth); ///g[v].depth not num!!!!!!
        }
        
    }
    s.push(u);
}
struct node2{
    long long sz;
    long long dp = 0;
    bool isArti = false;
    bool vis = false;
    int r;
    int p = -1;
    vi adj;
};

vector<node2> bct; ///block-cut tree
long long root = -1;
void dp(int u){
    if(bct[u].vis) return;
    bct[u].vis = true;
    bct[u].dp = bct[u].sz;
    bct[u].r = root;
    for(int i = 0;i < bct[u].adj.size();i++){
        int v = bct[u].adj[i];
        if(bct[v].vis) continue;
        bct[v].p = u;
        dp(v);
        bct[u].dp += bct[v].dp;
    }
}
int main()
{
    cin >> n >> m;
    ii edges[m];
    for(int i = 0;i < m;i++){
        int a, b;
        cin >> a >> b;
        a--;
        b--;
        g[a].adj.push_back(b);
        g[b].adj.push_back(a);
        edges[i] = ii(a,b);
    }

    for(int i = 0;i < n;i++){
        if(!g[i].vis){
            rootChildren = 0;
            g[i].depth = 0;
            dfs(i);
            if(rootChildren > 1) g[i].isArti = true;
            else g[i].isArti = false; ///this line is needed
        }
    }
    unordered_map<int,int> artis;
    for(int i = 0;i < n;i++){
        if(g[i].isArti){
            artis[i] = bct.size();
            node2 nn;
            nn.sz = 1;
            nn.isArti = true;
            bct.push_back(nn);
        }
    }


    for(int i = 0;i < biconnected.size();i++){
        node2 nn;
        nn.sz = biconnected[i].size();
        nn.isArti = false;
        for(unordered_set<int>::iterator it = biconnected[i].begin();it != biconnected[i].end();it++){
            if(artis.find(*it) != artis.end()){
                nn.adj.push_back(artis[*it]);
                bct[artis[*it]].adj.push_back(bct.size());
                nn.sz--;
            }
        }
        bct.push_back(nn);
    }
    for(int i = 0;i < bct.size();i++){
        root = i;
        dp(i);
    }

    long long ans = 0ll;
    for(int i = 0;i < bct.size();i++){
        vector<long long> branches;
        vector<long long> branchStart;
        long long total = 0ll;
        for(int j = 0;j < bct[i].adj.size();j++){
            if(bct[i].adj[j] != bct[i].p){
                branches.push_back(bct[bct[i].adj[j]].dp);
                branchStart.push_back(bct[bct[i].adj[j]].sz);
            }
        }
        if(bct[i].p >= 0){
            branches.push_back(bct[bct[i].r].dp - bct[i].dp);
            branchStart.push_back(bct[bct[i].p].sz);
        }
        for(int j = 0;j < branches.size();j++) total += branches[j];
        long long extra = 0ll;
        if(!bct[i].isArti) extra = max(0ll,(long long)(bct[i].adj.size())-2);
        for(int j = 0;j < branches.size();j++){

            ///branch1 to self or neighbor articulation point to branch2
            ans += branches[j] * (total - branches[j]) * (bct[i].sz + extra);

            ///branch to self to self or self to self to branch
            ans += 2 * (bct[i].sz) * (bct[i].sz - 1) * branches[j];


            if(bct[i].isArti){
                ///direct branch to self to same branch(not reverse) or its reverse
                ans += 2ll * bct[i].sz * branchStart[j] * (branches[j] - branchStart[j]);
                ///direct branch to self to direct or its reverse
                ans += bct[i].sz * (branchStart[j]) * (branchStart[j] - 1);

            }
        }

        ///self to self to self
        ans += (bct[i].sz) * (bct[i].sz - 1) * (bct[i].sz - 2);
    }
    cout << ans;
}

Compilation message (stderr)

count_triplets.cpp: In function 'void dfs(int)':
count_triplets.cpp:24:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |     for(int i = 0;i < g[u].adj.size();i++){
      |                   ~~^~~~~~~~~~~~~~~~~
count_triplets.cpp: In function 'void dp(int)':
count_triplets.cpp:71:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |     for(int i = 0;i < bct[u].adj.size();i++){
      |                   ~~^~~~~~~~~~~~~~~~~~~
count_triplets.cpp: In function 'int main()':
count_triplets.cpp:114:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::unordered_set<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  114 |     for(int i = 0;i < biconnected.size();i++){
      |                   ~~^~~~~~~~~~~~~~~~~~~~
count_triplets.cpp:127:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<node2>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  127 |     for(int i = 0;i < bct.size();i++){
      |                   ~~^~~~~~~~~~~~
count_triplets.cpp:133:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<node2>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  133 |     for(int i = 0;i < bct.size();i++){
      |                   ~~^~~~~~~~~~~~
count_triplets.cpp:137:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  137 |         for(int j = 0;j < bct[i].adj.size();j++){
      |                       ~~^~~~~~~~~~~~~~~~~~~
count_triplets.cpp:147:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  147 |         for(int j = 0;j < branches.size();j++) total += branches[j];
      |                       ~~^~~~~~~~~~~~~~~~~
count_triplets.cpp:150:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  150 |         for(int j = 0;j < branches.size();j++){
      |                       ~~^~~~~~~~~~~~~~~~~

• 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