Algorithms/Building.cpp at main · MohammadFahad1/Algorithms · GitHub

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
#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5;
int parent[N];
int group_size[N];

void dsu_initialize(int n)
{
    for (int i = 0; i <= n; i++)
    {
        parent[i] = -1;
        group_size[i] = 1;
    }
}

int dsu_find(int node)
{
    if (parent[node] == -1)
        return node;
    int leader = dsu_find(parent[node]);
    parent[node] = leader;
    return leader;
}

void dsu_union_by_size(int node1, int node2)
{
    int leaderA = dsu_find(node1);
    int leaderB = dsu_find(node2);
    if (leaderA != leaderB)
    {
        if (group_size[leaderA] > group_size[leaderB])
        {
            parent[leaderB] = leaderA;
            group_size[leaderA] += group_size[leaderB];
        }
        else
        {
            parent[leaderA] = leaderB;
            group_size[leaderB] += group_size[leaderA];
        }
    }
}

class Edge
{
public:
    int u, v;
    long long int w;
    Edge(int u, int v, long long int w)
    {
        this->u = u;
        this->v = v;
        this->w = w;
    }
};

bool cmp(Edge a, Edge b)
{
    return a.w < b.w;
}

int main()
{
    int n, e;
    cin >> n >> e;
    dsu_initialize(n);
    vector<Edge> edgeList;
    while (e--)
    {
        int u, v;
        long long int w;
        cin >> u >> v >> w;
        edgeList.push_back(Edge(u, v, w));
    }
    sort(edgeList.begin(), edgeList.end(), cmp);

    long long int totalCost = 0;
    int edgesUsed = 0;

    for (Edge ed : edgeList)
    {
        int leaderU = dsu_find(ed.u);
        int leaderV = dsu_find(ed.v);
        if (leaderU != leaderV)
        {
            dsu_union_by_size(ed.u, ed.v);
            totalCost += ed.w;
            edgesUsed++;
        }
    }

    if (edgesUsed == n - 1)
        cout << totalCost << endl;
    else
        cout << -1 << endl;

    return 0;
}