【PAT】A1034 Head of a Gang (30分)（圖的遍歷dfs）

1034 Head of a Gang (30分)

題目鏈接

思路：圖的深搜。

#include<iostream>
#include<map>
#include<cstring>
#include<algorithm>
using namespace std;

const int maxn = 2005;
const int inf = 0x3fffffff;

int Graph[maxn][maxn];
bool vis[maxn] = {false};
bool vis2[maxn] = {false};


int weight[maxn];
int n, k;
map<string, int>stringtoint;
map<int, string>inttostring;
int numperson = 0;
int total, maxName, addrName, maxValue;

struct Node{
	string name;
	int value;
}node[maxn];

void dfs(int u)
{
	vis[u] = true;
	vis2[u] = true;
	total ++; 
	if(weight[u] > maxName)
	{
		maxName = weight[u];
		addrName = u;
	}
	for(int i=0;i<numperson;i++){
		if(!vis[i] && Graph[u][i]!=inf){
			dfs(i);
		}
		if(!vis2[i] && Graph[u][i]!=inf)
			maxValue += Graph[u][i];
	}
	vis2[u] = false;
}

string intToStr(int id)
{
	map<string, int>::iterator it;
	for(it = stringtoint.begin(); it!=stringtoint.end(); it++)
		if(it->second == id)
			return it->first;
}

int strToInt(string str)
{
	if(stringtoint.find(str) != stringtoint.end()){
		return stringtoint[str];
	}
	else{
		stringtoint[str] = numperson;
		numperson ++;
		return numperson-1;
	}
}

int cmp(const Node &a, const Node &b)
{
	return a.name < b.name;
}

int main()
{
	fill(Graph[0], Graph[0] + maxn*maxn, inf);
	memset(weight, 0, sizeof(weight));
	cin>>n>>k;
	int id1, id2, value;
	string str1, str2;
	for(int i=0;i<n;i++)
	{
		cin>>str1>>str2>>value;
		id1 = strToInt(str1);
		id2 = strToInt(str2);
		weight[id1] += value;
		weight[id2] += value;
		if(Graph[id1][id2] == inf)
			Graph[id1][id2] = Graph[id2][id1] = value;
		else
		{
			Graph[id1][id2] += value;
			Graph[id2][id1] = Graph[id1][id2] ;
		}
	}
	int sum = 0;
	for(int i=0;i< numperson;i++)
	{
		total = 0;
		maxValue = 0;
		maxName = 0;
		if(!vis[i])
			dfs(i);
		if(total >= 3 && maxValue > k)
		{
			node[sum].value = total;
			node[sum++].name = intToStr(addrName);
		}
	}
	sort(node, node+sum, cmp);
	cout<<sum<<endl;
	for(int i=0;i<sum;i++)
		cout<<node[i].name<<" "<<node[i].value<<endl;
	return 0;
}

優化版本：

#include<iostream>
#include<map>
#include<cstring>
#include<algorithm>
using namespace std;

const int maxn = 2005;
const int inf = 0x3fffffff;

int Graph[maxn][maxn];
bool vis[maxn] = {false};
bool vis2[maxn] = {false};

int weight[maxn];//每個節點的總值 
int n, k;
map<string, int>stringtoint;
map<int, string>inttostring;
int numperson = 0;//總共多少人 
int total, maxName, addrName, maxValue;
//total:這次遍歷的連通塊節點數   maxName：標記節點值最大  
//addrName：節點值最大的下標  maxValue：此聯通快總價值 
map<string, int> gang; //存放結果 

void dfs(int u)
{
	vis[u] = true;
	vis2[u] = true;
	total ++; 
	if(weight[u] > maxName)
	{
		maxName = weight[u];
		addrName = u;
	}
	for(int i=0;i<numperson;i++){
		if(!vis[i] && Graph[u][i]!=inf){
			dfs(i);
		}
		if(!vis2[i] && Graph[u][i]!=inf)
			maxValue += Graph[u][i];
	}
	vis2[u] = false;
}

int strToInt(string str)
{
	if(stringtoint.find(str) != stringtoint.end()){
		return stringtoint[str];
	}
	else{
		stringtoint[str] = numperson;
		inttostring[numperson] = str;
		numperson ++;
		return numperson-1;
	}
}

int main()
{
	std::ios::sync_with_stdio(false);
	fill(Graph[0], Graph[0] + maxn*maxn, inf);
	memset(weight, 0, sizeof(weight));
	cin>>n>>k;
	int id1, id2, value;
	string str1, str2;
	for(int i=0;i<n;i++)
	{
		cin>>str1>>str2>>value;
		id1 = strToInt(str1);
		id2 = strToInt(str2);
		weight[id1] += value;
		weight[id2] += value;
		if(Graph[id1][id2] == inf)
			Graph[id1][id2] = Graph[id2][id1] = value;
		else
		{
			Graph[id1][id2] += value;
			Graph[id2][id1] = Graph[id1][id2] ;
		}
	}
	for(int i=0;i< numperson;i++)
	{
		total = 0;
		maxValue = 0;
		maxName = 0;
		if(!vis[i])
			dfs(i);
		if(total >= 3 && maxValue > k)
			gang[inttostring[addrName]] = total;
	}
	cout<<gang.size()<<endl;
	for(map<string, int>::iterator it=gang.begin();it != gang.end(); it++)
		cout<<it->first<<" "<<it->second<<endl;
	return 0;
}