Time Limit: 8000/4000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 4477 Accepted Submission(s): 1124
/*
HDU 5723 Abandoned country 最小生成树+搜索
problem:
给你n个点和m条边,让你求最少花费多少可以将所有点连通并求出任意两点的花费期望
solve:
第一个直接求最小生成树。主要是不懂它这个期望到底要求什么。看题解说的是深搜求出每条路用过
的次数来得到总花费。然后除以可能发生的次数
by——hhh
*/
#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <map>
#define lson ch[r][0]
#define rson ch[r][1]
#define ll long long
#define key_val ch[ch[root][1]][0]
using namespace std;
const int maxn = 100010;
const int inf = 0x3f3f3f3f;
int vis[maxn];
int f[maxn];
vector<pair<int,int>> q[maxn];
struct Edge
{
int u,v,w;
} edge[1000010];
int tot;
void add(int u,int v,int val)
{
edge[tot].u = u,edge[tot].v = v,edge[tot++].w = val;
}
bool cmp(Edge a,Edge b)
{
return a.w < b.w;
}
int fin(int x)
{
if(f[x] == -1) return x;
return f[x] = fin(f[x]);
}
ll cal(int n)
{
memset(f,-1,sizeof(f));
sort(edge,edge+tot,cmp);
ll cnt = 0,ans = 0;
for(int i = 0; i < tot; i++)
{
int u = edge[i].u;
int v = edge[i].v;
int w = edge[i].w;
int t1 = fin(u),t2 = fin(v);
if(t1 != t2)
{
ans = (ll)(ans + w);
f[t1] = t2;
cnt++;
q[u].push_back(make_pair(v,w));
q[v].push_back(make_pair(u,w));
}
if(cnt == n-1)
break;
}
// cout << cnt <<endl;
return ans;
}
int n;
double ans;
ll dfs(int now)
{
vis[now] = 1;
ll t = 0,ta = 0;
for(int i = 0; i < q[now].size(); i++)
{
ll v = q[now][i].first;
ll w = q[now][i].second;
if(!vis[v])
{
t = dfs(v);
ta += t;
ans = ans+1.0*t*(n-t)*w;
}
}
return ta+1;
}
int main()
{
int T,a,c,b;
// freopen("in.txt","r",stdin);
scanf("%d",&T);
while(T--)
{
int m;
ll tans;
tot = 0,ans = 0;
memset(vis,0,sizeof(vis));
scanf("%d%d",&n,&m);
for(int i =0; i <= n; i++)
q[i].clear();
for(int i = 1; i <= m; i++)
{
scanf("%d%d%d",&a,&b,&c);
add(a,b,c);
}
if(!n || !m)
{
printf("0 0.00\n");
continue;
}
tans = cal(n);
dfs(1);
double t = (1.0*n*(n-1)/2);
// cout <<ans <<" " <<t<<endl;
printf("%I64d %.2f\n",tans,ans/t);
}
return 0;
}
HDU 5723 Abandoned country 最小生成树+搜索
原文:http://www.cnblogs.com/Przz/p/5792156.html