1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
// Marcin Knapik

// Potyczki algorytmiczne - dzień 5 zadanie A1

#pragma GCC optimize "O3"
#include<bits/stdc++.h>
using namespace std;

#define f first
#define s second
#define sz(s) (int)s.size()
#define all(s) s.begin(), s.begin()
#define pb push_back
#define mp make_pair

#define ii pair<int, int>
#define ll long long
#define vi vector<int>
#define vii vector<ii>
#define vvi vector<vi>

int rep[1000007];

int Find(int x){
    return x == rep[x] ? x : rep[x] = Find(rep[x]);
}

void Union(int a, int b){
    a = Find(a);
    b = Find(b);

    rep[a] = b;
}

void dfs(int start, int przodek, int & pre, vi & low, vi & preorder, ll & ans, vvi & G){
    preorder[start] = pre++;
    low[start] = preorder[start];

    bool pierwszy = 1;
    for(auto & u : G[start]){
        if(u == przodek and pierwszy){
            pierwszy = false;
            continue;
        }
        if(preorder[u])
            low[start] = min(low[start], preorder[u]);
        else{
            dfs(u, start, pre, low, preorder, ans, G);
            low[start] = min(low[start], low[u]);
        }
    }

    if(przodek != -1 and low[start] == preorder[start])
        ans++;
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);

    int n, m;
    cin >> n >> m;
    vii kraw;

    for(int i = 0; i < m; i++){
        int a, b; cin >> a >> b;
        kraw.pb({a, b});
    }

    ll ans = 0;

    for(int i = 0; i < m; i++)
        for(int j = i + 1; j < m; j++){
            for(int k = 1; k <= n; k++)
                rep[k] = k;

            vvi G(n + 1);
            for(int k = 0; k < m; k++)
                if(i != k and j != k){
                    Union(kraw[k].f, kraw[k].s);
                    G[kraw[k].f].pb(kraw[k].s);
                    G[kraw[k].s].pb(kraw[k].f);
                }

            bool spoojny = 1;
            for(int k = 1; k < n; k++)
                spoojny &= Find(k) ==  Find(k + 1);
            
            if(!spoojny)
                ans += m - 2;
            else{
                vi low(n + 1);
                vi preorder(n + 1);
                int pre = 1;
                dfs(1, -1, pre, low, preorder, ans, G); 
            }
        }

    cout << ans / 3 << '\n';
}