noi.ac #39 MST

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;
}