算法思路

1.首先使用一个结构体存储所有边，以及边两端连接的顶点
2.对所有边进行排序
3.选出一条最短且不构成环的边，加入最小生成树集合，直到将所有点加入

使用了并查集的内容来判断两个点是否已经连通

算法应用题目样例：AcWing 859. Kruskal算法求最小生成树 https://www.acwing.com/problem/content/861/

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;

const int N = 100010, M = 200010, INF = 0x3f3f3f3f;

int n, m;
int p[N];

struct Edges
{
    int a, b, w;

    bool operator< (const Edges &W)const
    {
        return w < W.w;
    }
}edges[M];

int find(int x)
{
    if (p[x] != x) p[x] = find(p[x]);
    return p[x];
}

int kruskal()
{
    sort(edges, edges + m);

    for (int i = 1; i <= n; i ++ ) p[i] = i;    // 初始化并查集

    int res = 0, cnt = 0;
    for (int i = 0; i < m; i ++ )
    {
        int a = edges[i].a, b = edges[i].b, w = edges[i].w;

        a = find(a), b = find(b);
        if (a != b)
        {
            p[a] = b;
            res += w;
            cnt ++ ;
        }
    }

    if (cnt < n - 1) return INF;
    return res;
}

int main()
{
    scanf("%d%d", &n, &m);

    for (int i = 0; i < m; i ++ )
    {
        int a, b, w;
        scanf("%d%d%d", &a, &b, &w);
        edges[i] = {a, b, w};
    }

    int t = kruskal();

    if (t == INF) puts("impossible");
    else printf("%d\n", t);

    return 0;
}