#include <iostream>
#include <map>
#include <functional>
#include <initializer_list>
enum:int{ MAXVALUE = 999 }; //匿名枚举类型.
template<typename T>
struct Edge{
T startNode;
T endNode;
Edge()=default;
template<typename Ty>
Edge(const Ty& startNode_, const Ty& endNode_);
};
template<typename T>
template<typename Ty>
Edge<T>::Edge(const Ty& startNode_, const Ty& endNode_)
:startNode(startNode_),
endNode(endNode_)
{
//
}
template<typename T>
class Graph{
private:
std::map<T, std::map<T, int>> edges; //存储边.
std::map<T, int> vertices; //存储顶点.
Edge<T>* edgeArray;
bool flag;
int nodeNumber;
int edgeNumber;
template<typename Ty>
void initialize_single_source(const Ty& source_)noexcept;
template<typename Ty>
void relax(const Ty& source_)noexcept;
public:
template<typename Ty, unsigned int N>
Graph(const std::initializer_list<Ty>& vertices_, const Ty (&edges_)[N][3]);
~Graph();
template<typename Ty>
void Bellman_ford(const Ty& source_);
template<typename Ty>
void printPath(const Ty& source_)const;
};
template<typename T>
template<typename Ty, unsigned int N>
Graph<T>::Graph(const std::initializer_list<Ty>& vertices_, const Ty (&edges_)[N][3])
:flag(false)
{
if(N == 0 || vertices_.size() == 0){
throw std::runtime_error("it is empty in the graph");
}
this->nodeNumber = vertices_.size();
this->edgeNumber = N;
this->edgeArray = new Edge<Ty>[N]; //存储各个边的结点值.
typename std::initializer_list<Ty>::iterator it = vertices_.begin();
for(; it != vertices_.end(); ++it){
this->vertices[*it] = MAXVALUE;
}
for(int i=0; i<N; ++i){
Edge<Ty> edge(edges_[i][0], edges_[i][1]);
this->edges[edges_[i][0]][edges_[i][1]] = edges_[i][2];
this->edgeArray[i]=edge;
}
std::cout<<"out of constructor"<<std::endl;
}
template<typename T>
template<typename Ty>
void Graph<T>::initialize_single_source(const Ty& source_)noexcept
{
this->vertices[source_] = 0; //make the source node'degree of the graph 0; others is MAXVALUE.
}
template<typename T>
template<typename Ty>
void Graph<T>::relax(const Ty& source_)noexcept //noexcept show that the function can not throw exception;
{
for(int i=1; i<this->nodeNumber; ++i){
for(int j=0; j<this->edgeNumber; ++j){
if(this->vertices[source_] != MAXVALUE){
if(this->vertices[this->edgeArray[j].endNode] > this->vertices[this->edgeArray[j].startNode] + this->edges[this->edgeArray[j].startNode][this->edgeArray[j].endNode]){
this->vertices[this->edgeArray[j].endNode] = this->vertices[this->edgeArray[j].startNode] + this->edges[this->edgeArray[j].startNode][this->edgeArray[j].endNode];
//这两行写的比较长=.=
//其中this->vertices[this->edgeArray[j].startNode]获得的是该边的顶结点的distance(注:distance是指的是从当前顶点到source_这个给定顶点的距离).
//this->vertices[this->edgeArray[j].endNode]获得的是改变尾结点的distance.
}
}
}
}
}
template<typename T>
template<typename Ty>
void Graph<T>::Bellman_ford(const Ty& source_)
{
this->initialize_single_source(source_);
this->relax(source_);
for(int i=0; i<this->edgeNumber; ++i){
if(this->vertices[this->edgeArray[i].endNode] > this->vertices[this->edgeArray[i].startNode] + this->edges[this->edgeArray[i].startNode][this->edgeArray[i].endNode]){
this->flag = false;
break;
}
}
this->flag = true;
this->printPath(source_);
}
template<typename T>
Graph<T>::~Graph()
{
if( !this->edges.empty() ){
this->edges.clear();
}
if( !this->vertices.empty() ){
this->vertices.clear();
}
if(this->edgeArray != nullptr){
delete[] edgeArray;
this->edgeArray = nullptr;
}
}
template<typename T>
template<typename Ty>
void Graph<T>::printPath(const Ty& source_)const
{
if( this->flag == false ){
std::cout<<"there is not the shortest way."<<std::endl;
}else{
typename std::map<Ty, int>::const_iterator it = this->vertices.cbegin();
for(int i=0; i<this->nodeNumber; ++i){
std::cout<<source_<<" "<<it->first<<" "<<it->second<<std::endl;
}
}
}
int main()
{
int edges_[][3]={{0,1, 5}, {0,2, 8}, {0,3, -4}, {1,0, -2},
{2,1, -3}, {2,3, 9}, {3,1, 7}, {3,4, 2},
{4,0, 6}, {4,2, 7}};
Graph<int> myGraph({0, 1, 2, 3, 4}, edges_);
myGraph.Bellman_ford(3);
return 0;
}
