MST 模板题
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <string>
using namespace std;
const int N = 5e5 + 10;
#define LL long long
#define gc getchar()
#define Rep(i, a, b) for(int i = a; i <= b; i ++)
inline int read() {
int x = 0;
char c = gc;
while(c < '0' || c > '9') c = gc;
while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = gc;
return x;
}
struct Node {
int u, v, w;
bool operator < (const Node a) const {
return this-> w > a.w;
}
} E[N];
int fa[N];
LL Answer, tot;
int n, m;
int Get(int x) {
return fa[x] == x ? x : fa[x] = Get(fa[x]);
}
void Kruskal() {
int js = 0;
Rep(i, 1, m) {
int u = E[i].u, v = E[i].v, fau = Get(u), fav = Get(v);
if(fau != fav) {
fa[fau] = fav;
Answer += E[i].w;
js ++;
}
if(js == n - 1) return ;
}
}
int main() {
n = read(), m = read();
Rep(i, 1, m) {
E[i] = (Node) {
read(), read(), read()
};
tot += E[i].w;
}
Rep(i, 1, n) fa[i] = i;
sort(E + 1, E + m + 1);
Kruskal();
cout << tot - Answer;
return 0;
}