Create 5723_qq_18661257.cpp

From http://blog.csdn.net/qq_18661257/article/details/51958669

HDOJ/5723_qq_18661257.cpp

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+#include <cstring>
+#include <string>
+#include <cstdio>
+#include <cmath>
+#include <vector>
+#include <algorithm>
+using namespace std;
+const int MAXN = 1e6 + 5;
+typedef long long LL;
+struct edge {
+	int v, u, cost;
+	bool operator <(const edge &a) const {
+		return cost < a.cost;
+	}
+} es[MAXN];
+
+struct o {
+	int v, cost;
+	o() {}
+	o(int v, int cost):v(v), cost(cost) {}
+};
+
+int par[MAXN], ranks[MAXN];
+int sum[MAXN];
+bool vis[MAXN];
+int n, m;
+double minres;
+vector<o>G[MAXN];
+
+void init(int sizes) {//初始化
+	for(int i = 0; i <= sizes; i ++) {
+		par[i] = i;
+		ranks[i] = 1;
+		G[i].clear();
+	}
+}
+int find(int x) {
+	return par[x] == x ? x : par[x] = find(par[x]);
+}
+bool same(int x,int y) {
+	return find(x) == find(y);
+}
+void unite(int x,int y) {//连接
+	x = find(x);
+	y = find(y);
+	if(x == y)return ;
+	if(ranks[x] > ranks[y]) {
+		par[y] = x;
+	} else {
+		par[x] = y;
+		if(ranks[x] == ranks[y]) ranks[x] ++;
+	}
+}
+LL kruskal() {//最小生成树算法
+	sort(es,es + m);
+	init(n);
+	LL ret = 0;
+	for(int i=0; i<m; i++) {
+		edge e = es[i];
+		if(!same(e.u, e.v)) {
+			unite(e.u, e.v);
+			ret += e.cost;
+			G[e.u].push_back(o(e.v, e.cost));//将生成树中对应的点和边的值保存起来
+			G[e.v].push_back(o(e.u, e.cost));
+		}
+	}
+	return ret;
+}
+
+void DFS(int r, int f, int cost) {//得到最终的数学期望
+	if(vis[r]) return;
+	vis[r] = true;
+	sum[r] = 1;
+	for(int i = 0; i < G[r].size(); i ++) {
+		if(G[r][i].v == f) continue;
+		DFS(G[r][i].v, r, G[r][i].cost);
+		sum[r] += sum[G[r][i].v];
+	}
+	if(cost != -1)
+		minres += (LL)sum[r] * (LL)(n - sum[r]) * (LL)cost * 1.;//x * (n - 1) * cost即这条边的花费
+}
+
+int T;
+int main() {
+	scanf("%d", &T);
+	while(T --) {
+		scanf("%d%d", &n, &m);
+		for(int i = 0; i < m; i ++) {
+			scanf("%d%d%d",&es[i].v, &es[i].u, &es[i].cost);
+		}
+		if(n == 1){
+            printf("0 0.00\n");
+            continue;
+		}
+		LL minret = kruskal();
+		memset(sum, 0, sizeof(sum));
+		memset(vis, false, sizeof(vis));
+		minres = 0;
+		DFS(1, 1, -1);
+		printf("%I64d %.2lf\n", minret, minres * 2./ ((LL)n * (n - 1)));
+	}
+	return 0;
+}