UVA_820_Internet Bandwidth

#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0for (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;}

<pre name="code" class="cpp">#include<iostream>  #include<sstream>  #include<string>  #include<vector>  #include<list>  #include<set>  #include<map>#include<stack>  #include<queue>  #include<algorithm>  #include<numeric>  #include<cmath>#include<cstdio>#include<cstdlib>#include<cstring>#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 MaxVexNum = 1000;const int INF = 1000000000;class Edge{public:int to, capacity, flow;Edge(int t, int c, int f){to = t,capacity = c,flow = f;}};class Network{private:int vexnum, edgenum, source, destination,maxflow;vector<vector<Edge>>adjList;public:void addEdge(int from, int to, int cap){adjList[from].push_back({ to, cap, (int)adjList[to].size() });adjList[to].push_back({ from, 0, (int)adjList[from].size() - 1 });}Network(){adjList.resize(MaxVexNum);cin >> vexnum >> source >> destination >> edgenum;for (int i = 0; i < edgenum; i++){int from, to, capacity;cin >> from >> to >> capacity;addEdge(from, to, capacity);addEdge(to, from, capacity);}}int dfs(int src, int sink, int flow,vector<bool>&used){if (src == sink){return flow;}used[src] = true;for (int i = 0; i<adjList[src].size(); i++){Edge &edge = adjList[src][i];if (!used[edge.to] && edge.capacity>0){int minflow = dfs(edge.to, sink, std::min(flow, edge.capacity),used);if (minflow>0){edge.capacity -= minflow;adjList[edge.to][edge.flow].capacity += minflow;return minflow;}}}return 0;}void getMaxFlow(){maxflow = 0;while (1){vector<bool>used(MaxVexNum);int f = dfs(source, destination, INF,used);if (!f){return;}maxflow += f;}}void print(){cout << "The bandwidth is " << maxflow << '.' << endl<<endl;}};int main(){//freopen("input.txt", "r", stdin);//freopen("output.txt", "w", stdout);char ch; int count = 0;while ((ch=cin.get())!='0'){printf("Network %d\n", ++count);ungetc(ch,stdin);Network network;network.getMaxFlow();network.print();cin.get();}return 0;}