最小费用最大流算法
反复寻找费用最小路径，然后在该路径上使流量增大；寻找最小费用路径时，不考虑剩余容量为 0 的边；虽然网络流图是有向图，但是为了寻找包含反向边的路径，对每条正向边都有可能生成出反向边（当正向边上有流量时，就有容量等于流量的反向边）；
NetworkFlowGraph.h 类头文件：
//============================================================================// Name : MinCostFlow.cpp// Author : Qichi// Version :// Copyright : Copyright QiChi// Description : Hello World in C++, Ansi-style//============================================================================#include <iostream>#include "NetworkFlowGraph.h"using namespace std;int main() {double flow, cost;NetworkFlowGraph *inst = new NetworkFlowGraph(5,0,4);inst->insert(0,1,10,4);inst->insert(0,2,8,1);inst->insert(2,1,5,2);inst->insert(2,3,10,3);inst->insert(1,3,2,6);inst->insert(1,4,7,1);inst->insert(3,4,4,2);inst->min_cost_max_flow(flow, cost);cout << flow << ":" << cost << endl;delete inst;return 0;}