最小生成树Kruskal

Kruskal时间复杂度（mlogm）

算法思路：每次找到最小边如果不在树的集合中就添加进去

#include <iostream>
#include <string>
#include <cstring>
#include <queue>
#include <cstdio>
#include <algorithm>
#define FT(a, b) memset(a, b, sizeof(a))
using namespace std;

const int M = 2e5 + 10;
int n, m, f[M];
struct node
{
    int u, v, w;
    bool operator<(const node &x) const
    {
        return x.w > w;
    }
} e[M];
int find(int x)
{
    if (f[x] != x)
        f[x] = find(f[x]);
    return f[x];
}
int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 0; i < m; i++)
    {
        scanf("%d%d%d", &e[i].u, &e[i].v, &e[i].w);
    }
    sort(e, e + m);
    int cnt = 0, ans = 0;
    for (int i = 1; i <= n; i++)
        f[i] = i;
    for (int i = 0; i < m; i++)
    {
        int u = e[i].u, v = e[i].v, w = e[i].w;
        int fu = find(u), fv = find(v);
        if (fu != fv)
        {
            f[fu] = fv;
            cnt++;
            ans += w;
        }
    }
    if (cnt < n - 1)
        puts("impossible");
    else
        printf("%d\n", ans);
}