【WEISS算法书】Prim算法

最新推荐文章于 2025-07-30 14:22:39 发布

array020

最新推荐文章于 2025-07-30 14:22:39 发布

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CC 4.0 BY-SA版权

文章标签：算法 table null delete insert

本文链接：https://blog.youkuaiyun.com/damacheng/article/details/6473379

本文介绍了一种使用普里姆算法求解最小生成树的方法。通过详细的代码示例，展示了如何构建非定向图并利用最小堆来寻找最小生成树的过程。文章涵盖了数据结构的设计、初始化及销毁等关键环节。

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写这玩意乱写一气。。估计连自己都看不太懂了。。先留在这儿先。。免得程序给弄丢了。。

Code:

#include <iostream>
#include <string>
using namespace std;
struct HeapStruct
{
int Capacity;
int size;
int *Elements;
};
typedef HeapStruct* PriorityQueue;
PriorityQueue Initialize(int MaxElements)
{
PriorityQueue pq=(PriorityQueue)malloc(sizeof(HeapStruct));
if(pq==NULL)
{
cout<<"Bad Memory Allocated!"<<endl;
exit(1);
}
/*if(MaxElements<5)
{
cout<<"Too Few!"<<endl;
return NULL;
}
*/
pq->size=0;
pq->Capacity=MaxElements;
pq->Elements=(int*)malloc(sizeof(int)*pq->Capacity+1);
if(pq->Elements==NULL)
{
cout<<"Bad Memory Allocated!"<<endl;
exit(1);
}
pq->Elements[0]=-10000;
return pq;
}
void Destroy(PriorityQueue pq)
{
free(pq->Elements);
free(pq);
}
bool IsFull(PriorityQueue pq)
{
return pq->size==pq->Capacity;
}
bool IsEmpty(PriorityQueue pq)
{
return pq->size==0;
}
void Insert(int data,PriorityQueue pq)
{
if(IsFull(pq))
{
cout<<"Full!"<<endl;
return;
}
int i;
for(i=++pq->size;pq->Elements[i/2]>data;i/=2)
{
pq->Elements[i]=pq->Elements[i/2];
}
pq->Elements[i]=data;
}
int DeleteMin(PriorityQueue pq)
{
if(IsEmpty(pq))
{
cout<<"Empty!"<<endl;
exit(1);
}
int i=1;
int child;
int minElement=pq->Elements[1];
int lastElement=pq->Elements[pq->size--];
while(i*2<=pq->size)
{
child=i*2;
if(child!=pq->size && pq->Elements[child]>pq->Elements[child+1])
{
++child;
}
if(pq->Elements[child]<lastElement)
{
pq->Elements[i]=pq->Elements[child];
}
else
{
break;
}
i=child;
}
pq->Elements[i]=lastElement;
return minElement;
}
struct VertexNode
{
VertexNode * nextVertex;
string edge;
int weight;
VertexNode(string e,int w):weight(w),edge(e){}
};
struct Vertex
{
string name;
VertexNode *first;
Vertex(string n):name(n){first=NULL;}
};
typedef Vertex* ab;
struct Entry;
struct NonDireGraph
{
ab *vertice;
int verNum;
NonDireGraph(int vn):verNum(vn)
{
vertice=new ab[verNum];
for(int i=0;i<verNum;i++)
{
cout<<"给个名字";
string tmp;
cin>>tmp;
vertice[i]=new Vertex(tmp);
for(;;)
{
cout<<"要加边咩？"<<endl;
char tmpC;
cin>>tmpC;
if(tmpC == 'N')
{
break;
}
cout<<"给出边名字"<<endl;
string tmpS;
cin>>tmpS;
cout<<"给出权值"<<endl;
int tmpW;
cin>>tmpW;
VertexNode *tmpV=new VertexNode(tmpS,tmpW);
tmpV->nextVertex=vertice[i]->first;
vertice[i]->first=tmpV;
}
}
}
~NonDireGraph()
{
for(int i=0;i<verNum;i++)
{
while(vertice[i]->first!=NULL)
{
VertexNode *tmp=vertice[i]->first;
vertice[i]->first=tmp->nextVertex;
delete tmp;
}
delete vertice[i];
}
delete [] vertice;
}
void AddKnownVertex(const string &name,Entry *e);
int FindIndexByName(const string &name)
{
for(int i=0;i<verNum;i++)
{
if(vertice[i]->name==name)
{
return i;
}
}
return -1;
}
};
struct Entry
{
string name;
int isVisited;
int currentWeight;
string lastVisited;
Entry(){}
Entry(string n,bool iv,int cw,string lv):name(n),isVisited(iv),currentWeight(cw),lastVisited(lv){}
};
Entry * InitializeEntry(const NonDireGraph &g)
{
Entry *retEntry=new Entry[g.verNum];
for(int i=0;i<g.verNum;i++)
{
retEntry[i].name=g.vertice[i]->name;
retEntry[i].isVisited=0;
retEntry[i].currentWeight=30000;
retEntry[i].lastVisited="";
}
return retEntry;
}
void DisposeEntry(Entry *e)
{
delete [] e;
}
void NonDireGraph::AddKnownVertex(const string &name,Entry *e)
{
int i=FindIndexByName(name);
for(VertexNode *vn=vertice[i]->first;vn!=NULL;vn=vn->nextVertex)
{
for(int j=0;j<verNum;j++)
{
if(e[j].isVisited==0 && e[j].name==(vn->edge))
{
int previousWeight=0;
for(int k=0;k<verNum;k++)
{
if(e[k].name==name)
{
previousWeight=e[k].currentWeight;
}
}
if(e[j].currentWeight>vn->weight+previousWeight)
{
e[j].currentWeight=vn->weight+previousWeight;
e[j].lastVisited=name;
}
}
}
}
}
Entry * Prim(NonDireGraph &g,const string &startName)
{
Entry *table=InitializeEntry(g);
for(int i=0;i<g.verNum;i++)
{
if(table[i].name==startName)
{
table[i].currentWeight=0;
table[i].isVisited=1;
g.AddKnownVertex(startName,table);
}
}
for(;;)
{
PriorityQueue pq=Initialize(g.verNum);
int i;
for(i=0;i<g.verNum;i++)
{
if(!table[i].isVisited)
{
Insert(table[i].currentWeight,pq);
}
}
int min=DeleteMin(pq);
for(i=0;i<g.verNum;i++)
{
if(table[i].currentWeight==min)
{
table[i].isVisited=1;
g.AddKnownVertex(table[i].name,table);
}
}
Destroy(pq);
for(i=0;i<g.verNum;i++)
{
if(table[i].isVisited==0)
{
continue;
}
}
break;
}
return table;
}
int main()
{
NonDireGraph ndg(7);
Entry *table=Prim(ndg,"V1");
for(int i=0;i<ndg.verNum;i++)
{
cout<<table[i].name<<' ';
cout<<table[i].isVisited<<' ';
cout<<table[i].currentWeight<<' ';
cout<<table[i].lastVisited<<endl;
}
DisposeEntry(table);
return 0;
}