PAT 1034. Head of a Gang (30)

题目地址:http://pat.zju.edu.cn/contests/pat-a-practise/1034

此题考查并查集的应用，要熟悉在合并的时候存储信息：

#include <iostream>
#include <string>
#include <map>
#include <vector>
#include <algorithm>
#include <cstddef>
using namespace std;

struct Person
{
    int personalTime;
    int gangTime;//记录以当前person为根的集合的gang 的总的通话时间
    vector<string> members;//记录以当前person为根的集合的gang members
    string root;
    Person()
    {
        personalTime=0;
        gangTime=0;
        root="-1";
    }
};

map<string,Person> tree;//并查集
map<string,int> gangs;//符合条件的gang

string findRoot(string index)
{
    if(tree[index].root=="-1") return index;
    else 
    {
        string tmp=findRoot(tree[index].root);
        tree[index].root=tmp;
        return tmp;
    }
}

string findHead(string root)//找出当前gang中具有最大weight的为gang head
{
    vector<string> members=tree[root].members;
    string gangHead=root;
    int maxPersonalTime=tree[root].personalTime;
    for(vector<string>::iterator iter=members.begin();iter!=members.end();++iter)
    {
        if(tree[*iter].personalTime>maxPersonalTime)
        {
            gangHead=*iter;
            maxPersonalTime=tree[*iter].personalTime;
        }
    }
    return gangHead;
}

int _tmain(int argc, _TCHAR* argv[])
{
    int N,K;
    cin>>N>>K;
    int i;
    string Name1,Name2,root1,root2;
    int Time;
    for(i=0;i<N;++i)
    {
        cin>>Name1>>Name2>>Time;
        if(tree[Name1].members.size()==0)
        {
            tree[Name1].members.push_back(Name1);
        }
        if(tree[Name2].members.size()==0)
        {
            tree[Name2].members.push_back(Name2);
        }
        tree[Name1].personalTime+=Time;
        tree[Name2].personalTime+=Time;
        root1=findRoot(Name1);
        root2=findRoot(Name2);
        if(root1!=root2)
        {
            tree[root1].root=root2;
            tree[root2].gangTime+=Time;
            tree[root2].gangTime+=tree[root1].gangTime;
            tree[root2].members.insert(tree[root2].members.end(),tree[root1].members.begin(),tree[root1].members.end());
        }
        else
        {
            tree[root2].gangTime+=Time;
        }
    }
    for(map<string,Person>::iterator iter=tree.begin();iter!=tree.end();++iter)
    {
        if(iter->second.root=="-1"&&iter->second.members.size()>2&&iter->second.gangTime>K)
        {
            string head=findHead(iter->first);
            gangs[head]=iter->second.members.size();
        }
    }
    size_t size=gangs.size();
    cout<<size<<endl;
    if(0==size)
    {
        return 0;
    }
    for(map<string,int>::iterator iter=gangs.begin();iter!=gangs.end();++iter)
    {
        cout<<iter->first<<" "<<iter->second<<endl;
    }
    return 0;
}