POJ:3371 Connect the Cities(最小生成树）

Posted 2021-02-03 dwvictor

http://acm.hdu.edu.cn/showproblem.php?pid=3371

AC代码：

/**
/*@author Victor
/* C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;

const int maxn=500+10;
struct Edge
{
    int from,to,dist;
    Edge(int f,int t,int d):from(f),to(t),dist(d) {}
    bool operator <(const Edge& a)
    {
        return dist<a.dist;
    }
};
vector<Edge>edges;
int pre[maxn],T[maxn];
//并查集
int find(int x)
{
    int i=x;
    while(pre[i]!=i)
        i=pre[i];
    int j=x,k;
    while(j!=pre[j])
    {
        k=pre[j];
        pre[j]=i;
        j=k;
    }
    return i;
}
void joint(int x,int y)
{
    if(find(x)!=find(y))
        pre[find(x)]=find(y);
}
int kruskal()
{
    int sum=0;
    sort(edges.begin(),edges.end());
    for(int i=0; i<edges.size(); i++)
    {
        int x=find(edges[i].from),y=find(edges[i].to);
        if(x!=y)
        {
            sum+=edges[i].dist;
            pre[x]=y;
        }
    }
    return sum;
}
int main()
{
    int n,m,k,Case;
    scanf("%d",&Case);
    while(Case--)
    {
        scanf("%d%d%d",&n,&m,&k);
        for(int i=1; i<=n; i++)
            pre[i]=i;
        edges.clear();
        for(int i=0; i<m; i++)
        {
            int f,t,d;
            scanf("%d%d%d",&f,&t,&d);
            edges.push_back(Edge(f,t,d));
        }
        for(int i=0; i<k; i++)
        {
            int t;
            scanf("%d",&t);
            for(int j=0; j<t; j++)
                scanf("%d",&T[j]);
            for(int j=1; j<t; j++)
                joint(T[0],T[j]);
        }
        int ans=kruskal();
        //通过并查集判断是否联通
        bool mark=true;
        for(int i=2; i<=n; i++)
            if(find(1)!=find(i))
            {
                mark=false;
                break;
            }
        if(mark==true)
            printf("%d
",ans);
        else
            printf("-1
");
    }
    return 0;
}