方法二：

//方法2：
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e4;
struct Edge {
    int u, v, w;
};
Edge b[MAXN];
int pa[MAXN], size[MAXN];
int n, m, total, sum;

void init() {
    for (int i = 0; i < n; i++) {
        pa[i] = i;
        size[i] = 1;
    }
}

//查找x的树根
int find(int x) {
    if (pa[x] != x) pa[x] = find(pa[x]);
    return pa[x];
}

//合并两个集合/两棵树
void join(int x, int y) {
    int px = find(x), py = find(y);
    if (px == py) return;
    if (size[px] < size[py]) swap(px, py);
    pa[py] = px;  //小的树py接到大树px上
    size[px] += size[py];
}

bool cmp(Edge x, Edge y) { return x.w < y.w; }
void kruskal() {
    int cnt = 0;
    for (int i = 0; i < m; i++) {
        int u = b[i].u, v = b[i].v, w = b[i].w;
        if (find(u) != find(v)) {
            join(u, v);
            cnt++;
            sum += w;
            if (cnt == n - 1) break;
        }
    }
}
int main() {
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        cin >> b[i].u >> b[i].v >> b[i].w;
        total += b[i].w;
    }
    init();
    sort(b, b + m, cmp);
    kruskal();
    cout << total - sum << endl;
    return 0;
}

方法一：

//方法1：
#include <bits/stdc++.h>
using namespace std;
const int N = 101, M = 1e4 + 5;
int n, k;
int pa[N], size1[N];

struct Edge {
    int i, j, m;
} a[M];

bool cmp(Edge e1, Edge e2) {
    return e1.m < e2.m;
}

void init() {
    for(int i=0; i<n; i++) {
        pa[i] = i;
        size1[i] = 1;
    }
}

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

void join(int x, int y) {
    int px = find(x), py = find(y);
    if(px == py) return;
    if(size1[px] < size1[py]) swap(px, py);
    pa[py] = px;
    size1[px] += size1[py];
}

int main(){
    cin>>n>>k;
    init();
    for(int i=0; i<k; i++) {
        cin>>a[i].i>>a[i].j>>a[i].m;
    }
    sort(a, a+k, cmp);
    
    int sum = 0;
    for(int i=0; i<k; i++) {
        int px = find(a[i].i), py = find(a[i].j);
        if(px != py) join(px, py);
        else sum += a[i].m;
    }
    cout<<sum;
    return 0;
}