Counting Triangles Ugly

// Knapsack DP is harder than FFT.
#include<bits/stdc++.h>
using namespace std;
typedef long long ll; typedef pair<int,int> pii; typedef pair<ll,ll> pll;
#define ff first
#define ss second
#define pb emplace_back
#define AI(x) begin(x),end(x)
template<class I>bool chmax(I&a,I b){return a<b?(a=b,true):false;}
template<class I>bool chmin(I&a,I b){return b<a?(a=b,true):false;}
#ifdef OWO
#define debug(args...) SDF(#args, args)
#define OIU(args...) ostream& operator<<(ostream&O,args)
#define LKJ(S,B,E,F) template<class...T>OIU(S<T...>s){O<<B;int c=0;for(auto i:s)O<<(c++?", ":"")<<F;return O<<E;}
LKJ(vector,'[',']',i)LKJ(deque,'[',']',i)LKJ(set,'{','}',i)LKJ(multiset,'{','}',i)LKJ(unordered_set,'{','}',i)LKJ(map,'{','}',i.ff<<':'<<i.ss)LKJ(unordered_map,'{','}',i.ff<<':'<<i.ss)
template<class...T>void SDF(const char* s,T...a){int c=sizeof...(T);if(!c){cerr<<"\033[1;32mvoid\033[0m\n";return;}(cerr<<"\033[1;32m("<<s<<") = (",...,(cerr<<a<<(--c?", ":")\033[0m\n")));}
template<class T,size_t N>OIU(array<T,N>a){return O<<vector<T>(AI(a));}template<class...T>OIU(pair<T...>p){return O<<'('<<p.ff<<','<<p.ss<<')';}template<class...T>OIU(tuple<T...>t){return O<<'(',apply([&O](T...s){int c=0;(...,(O<<(c++?", ":"")<<s));},t),O<<')';}
#else
#pragma GCC optimize("Ofast")
#define debug(...) ((void)0)
#endif

const int N = 100001;
int n, m;
int deg[N];
vector<int> adj[N];
vector<pii> edges;
map<int, bitset<N>> jizz;


signed main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin >> n >> m;
    for(int u, v, i = 0; i < m; ++i){
        cin >> u >> v;
        adj[u].pb(v); adj[v].pb(u);
        ++deg[u], ++deg[v];
        edges.pb(u, v);
    }

    int k = ceil(sqrt(m));
    for(int i = 0; i < n; ++i){
        if(deg[i] <= k) sort(AI(adj[i]));
        else{
            jizz[i] = bitset<N>();
            for(int j: adj[i]) jizz[i][j] = true;
        }
    }

    int ans = 0;
    for(auto [u, v]: edges){
        if(deg[u] > deg[v]) swap(u, v);
        if(deg[u] <= k and deg[v] <= k){
            int i = 0, j = 0;
            while(i < deg[u] and j < deg[v]){
                if(adj[u][i] == adj[v][j]) ++i, ++j, ++ans;
                else if(adj[u][i] < adj[v][j]) ++i;
                else ++j;
            }
        } else {
            for(int w: adj[u]) if(jizz[v][w]) ++ans;
        }
    }
    cout << ans / 3 << '\n';

    return 0;
}