hdu 5723(最小生成树)

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#include <bits/stdc++.h>#pragma comment(linker, "/STACK:102400000,102400000")using namespace std;#define LL long long#define pii pair<int,int>#define MP make_pair#define ls i << 1#define rs ls | 1#define md (ll + rr >> 1)#define lson ll, md, ls#define rson md + 1, rr, rs#define Pi acos(-1.0)#define mod 1000000007#define eps 1e-12#define inf 0x3f3f3f3f#define N 200010#define M 1000020struct edge{    int u, v, w;    void input(){        scanf("%d%d%d", &u, &v, &w);    }}ee[M];int n, m, fa[N], c[M], id[M];int fst[N], vv[M], nxt[M], cost[M], e;int sz[N];LL ans;void init(){    memset(fst, -1, sizeof fst); e = 0;}void add(int u, int v, int w){    vv[e] = v, nxt[e] = fst[u], cost[e] = w, fst[u] = e++;}void dfs(int u, int p){    sz[u] = 1;    for(int i = fst[u]; ~i; i = nxt[i]){        int v = vv[i];        if(v == p) continue;        dfs(v, u);        sz[u] += sz[v];        ans += 1LL * (n - sz[v]) * sz[v] * cost[i];    }}int find(int x){    if(fa[x] != x) fa[x] = find(fa[x]);    return fa[x];}int main(){    int cas;    scanf("%d", &cas);    while(cas--){        ans = 0;        scanf("%d%d", &n, &m);        memset(c, 0, sizeof c);        for(int i = 1; i <= m; ++i){            ee[i].input();            c[ee[i].w]++;        }        for(int i = 1; i < M; ++i) c[i] += c[i-1];        for(int i = 1; i <= m; ++i)            id[c[ee[i].w]--] = i;        for(int i = 0; i <= n; ++i) fa[i] = i;        init();        LL tot = 0;        for(int i = 1; i <= m; ++i){            int x = id[i], u = ee[x].u, v = ee[x].v, w = ee[x].w;            if(find(u) == find(v)) continue;            fa[find(u)] = find(v);            add(u, v, w);            add(v, u, w);            tot += w;        }        dfs(1, -1);        double ret = 1.0 * ans / n / (n -1) * 2;        printf("%lld %.2f\n", tot, ret);    }    return 0;}
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