TheAlgorithms-C-Plus-Plus/graph/kruskal.cpp

#include <iostream>
//#include <boost/multiprecision/cpp_int.hpp>
// using namespace boost::multiprecision;
const int mx = 1e6 + 5;
const long int inf = 2e9;
typedef long long ll;
#define rep(i, n) for (i = 0; i < n; i++)
#define repp(i, a, b) for (i = a; i <= b; i++)
#define pii pair<int, int>
#define vpii vector<pii>
#define vi vector<int>
#define vll vector<ll>
#define r(x) scanf("%d", &x)
#define rs(s) scanf("%s", s)
#define gc getchar_unlocked
#define pc putchar_unlocked
#define mp make_pair
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define endl "\n"
#define fast                          \
    ios_base::sync_with_stdio(false); \
    cin.tie(NULL);                    \
    cout.tie(NULL);
using namespace std;
void in(int &x)
{
    register int c = gc();
    x = 0;
    int neg = 0;
    for (; ((c < 48 || c > 57) && c != '-'); c = gc())
        ;
    if (c == '-')
    {
        neg = 1;
        c = gc();
    }
    for (; c > 47 && c < 58; c = gc())
    {
        x = (x << 1) + (x << 3) + c - 48;
    }
    if (neg)
        x = -x;
}
void out(int n)
{
    int N = n, rev, count = 0;
    rev = N;
    if (N == 0)
    {
        pc('0');
        return;
    }
    while ((rev % 10) == 0)
    {
        count++;
        rev /= 10;
    }
    rev = 0;
    while (N != 0)
    {
        rev = (rev << 3) + (rev << 1) + N % 10;
        N /= 10;
    }
    while (rev != 0)
    {
        pc(rev % 10 + '0');
        rev /= 10;
    }
    while (count--) pc('0');
}
ll parent[mx], arr[mx], node, edge;
vector<pair<ll, pair<ll, ll>>> v;
void initial()
{
    int i;
    rep(i, node + edge) parent[i] = i;
}
int root(int i)
{
    while (parent[i] != i)
    {
        parent[i] = parent[parent[i]];
        i = parent[i];
    }
    return i;
}
void join(int x, int y)
{
    int root_x = root(x);  // Disjoint set union by rank
    int root_y = root(y);
    parent[root_x] = root_y;
}
ll kruskal()
{
    ll mincost = 0, i, x, y;
    rep(i, edge)
    {
        x = v[i].second.first;
        y = v[i].second.second;
        if (root(x) != root(y))
        {
            mincost += v[i].first;
            join(x, y);
        }
    }
    return mincost;
}
int main()
{
    fast;
    while (1)
    {
        int i, j, from, to, cost, totalcost = 0;
        cin >> node >> edge;  // Enter the nodes and edges
        if (node == 0 && edge == 0)
            break;  // Enter 0 0 to break out
        initial();  // Initialise the parent array
        rep(i, edge)
        {
            cin >> from >> to >> cost;
            v.pb(mp(cost, mp(from, to)));
            totalcost += cost;
        }
        sort(v.begin(), v.end());
        // rep(i,v.size())
        // 	cout<<v[i].first<<"  ";
        cout << kruskal() << endl;
        v.clear();
    }
    return 0;
}