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#include<iostream>
#include<sstream>
#include<string>
#include<vector>
#include<list>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<algorithm>
#include<numeric>
#include<cmath>
#pragma warning(disable:4996)
using std::cin;
using std::cout;
using std::endl;
using std::stringstream;
using std::string;
using std::vector;
using std::list;
using std::pair;
using std::set;
using std::multiset;
using std::map;
using std::multimap;
using std::stack;
using std::queue;
using std::priority_queue;
class Edge
{
public:
int from,to, flow, capacity;
Edge(const int &v,const int &a, const int &c,const int &f)
{
from=v,to = a, capacity = c,flow=f;
}
};
class Network
{
private:
int n, m;//表示顶点个数和边个数
int src, sink;//表示源点和汇点
int max_flow;//最大流
vector<Edge>edge;//边数的两倍
vector<vector<int>>adjList;//邻接表
public:
void addEdge(const int &from,const int &to,const int &capacity)
{
edge.push_back({from,to,capacity,0});
adjList[from].push_back(edge.size()-1);
edge.push_back({to,from,0,0});
adjList[from].push_back(edge.size() - 1);
}
Network(const int &N)
{
max_flow = 0,n = N;
cin >> src >> sink >> m;
adjList.resize(n + 1);
for (int i = 0; i < m; i++)
{
int from, to, capacity;
cin >> from >> to >> capacity;
addEdge(from,to,capacity);
addEdge(to, from, capacity);
}
}
void getMaxFlow()
{
vector<int>path(n + 1);
while (1)
{
vector<int>augument(n + 1);
queue<int>Q;
Q.push(src);
augument[src] = 2000000000;
while (!Q.empty())
{
auto x = Q.front();
Q.pop();
for (int i = 0; i < adjList[x].size(); i++)
{
Edge&e = edge[adjList[x][i]];
if (!augument[e.to]&&e.capacity>e.flow)
{
path[e.to] = adjList[x][i];
augument[e.to] = std::min(augument[x],e.capacity-e.flow);
Q.push(e.to);
}
}
if (augument[sink])
{
break;
}
}
if (!augument[sink])
{
break;
}
for (auto u = sink;u!=src;u=edge[path[u]].from)
{
edge[path[u]].flow += augument[sink];
edge[path[u]^1].flow-= augument[sink];
}
max_flow += augument[sink];
}
}
void printMaxFlow()
{
cout << "The bandwidth is " << max_flow << "." << endl<<endl;
}
};
int main()
{
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
int count = 0,n;
while (cin >> n&&n)
{
cout << "Network " << ++count << endl;
Network network(n);
network.getMaxFlow();
network.printMaxFlow();
}
return 0;
}
#include<iostream>
#include<sstream>
#include<string>
#include<vector>
#include<list>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<algorithm>
#include<numeric>
#include<cmath>
#pragma warning(disable:4996)
using std::cin;
using std::cout;
using std::endl;
using std::stringstream;
using std::string;
using std::vector;
using std::list;
using std::pair;
using std::set;
using std::multiset;
using std::map;
using std::multimap;
using std::stack;
using std::queue;
using std::priority_queue;
const int infinity =1000000000;
class Network
{
private:
int vexnum, edgenum, maxflow, source, destination;
vector<int>remnant, path;
vector<vector<int>>flow, capacity;
public:
void addEdge()
{
int from, to, c; cin >> from >> to >> c;
capacity[from - 1][to - 1] += c;
capacity[to - 1][from - 1] += c;
}
Network(const int &n)
{
vexnum = n;
cin >> source >> destination >> edgenum;
source--, destination--;
flow.resize(vexnum, (vector<int>)vexnum), capacity.resize(vexnum, (vector<int>)vexnum);//最开始每条边的流量都是0
for (int i = 0; i < edgenum; i++)
{
addEdge();
}
}
void getMaxFlow_EK()
{
maxflow = 0;
queue<int> Q;
while (!Q.empty())
{
Q.pop();
}
vector<int>path(vexnum);
while (true)
{
vector<int>remnant(vexnum);//残余流量得变0,一开始所有点都没流入对吧
remnant[source] = infinity; //源点嘛,剩余流量无限是必须的...
Q.push(source); //从源点开始进行BFS找增广路
int from, to;
while (!Q.empty())
{
from = Q.front();Q.pop();
for (to = 0; to < vexnum; to++)//遍历所有点,找可行边
{
if (!remnant[to] && capacity[from][to]>flow[from][to])
{ //该点剩余流量为0 且 容量大于流量,也就是找到了新的结点
path[to] = from; //找到新结点,父节点得记录一下吧
Q.push(to);
remnant[to] = std::min(remnant[from], capacity[from][to] - flow[from][to]); //如果u的剩余流量能填满uv就填满,不能的话就把u这点的流量全部流向uv
}
}
}
if (remnant[destination] == 0) //如果当前已经是最大流,汇点没有残余流量
{
break;
}
for (from = destination; from != source; from = path[from])
{ //如果还能增广,那么回溯,从汇点往回更新每条走过的边的流量
flow[path[from]][from] += remnant[destination]; //更新正向流量 （注意这里更新的是流量，而不是容量）
flow[from][path[from]] -= remnant[destination]; //更新反向流量
}
maxflow += remnant[destination];
}
}
void print()
{
cout << "The bandwidth is " << maxflow << "." << endl<<endl;
}
};
int main()
{
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
int n,count=0;
while (cin>>n&&n)
{
cout << "Network " << ++count << endl;
Network network(n);
network.getMaxFlow_EK();
network.print();
}
return 0;
}标签：
原文地址：http://blog.csdn.net/cxy7tv/article/details/51361313
