[알고리즘 C언어] 7.3.3 프림 알고리즘 소스 코드

다음은 C언어로 작성한 프림(Prim) 알고리즘 소스 코드입니다. 프림 알고리즘은 그래프에서 최소신장트리를 만드는 대표적인 탐욕(Greedy) 알고리즘입니다.

//Array.h
#pragma once
typedef void * Element;
typedef struct _Array Array;
struct _Array
{
	Element *base;
	int capacity;
	int usage;
};
typedef Element *Iterator;

Array *New_Array();
void Delete_Array(Array *arr);
void Array_SetSize(Array *arr,int capacity,Element data);
void Array_PushBack(Array *arr,Element data);
void Array_Insert(Array *arr,Iterator pos,Element data);
void Array_SetAt(Array *arr,int index,Element data);
Element Array_GetAt(Array *arr,int index);
Iterator Array_Begin(Array *arr);
Iterator Array_End(Array *arr);
void Array_Erase(Array *arr,Iterator pos);

//Array.c
#include "Array.h"
#include <malloc.h>
#include <memory.h>
Array *New_Array()
{
	Array *arr = 0;
	arr = (Array *)malloc(sizeof(Array));
	arr->base = 0;
	arr->capacity = arr->usage = 0;
	return arr;
}
void Delete_Array(Array *arr)
{
	if(arr->base)
	{
		free(arr->base);
	}
	free(arr);
}
void Array_SetSize(Array *arr,int capacity,Element data)
{		
	arr->capacity = capacity;
	arr->base = (Element *)realloc(arr->base,sizeof(Element)*arr->capacity);
	for(    ;arr->usage<arr->capacity; arr->usage++)
	{
		arr->base[arr->usage] = data;
	}
}
void Array_PushBack(Array *arr,Element data)
{
	Iterator at = Array_End(arr);
	Array_Insert(arr,at,data);
}
void Array_Insert(Array *arr,Iterator pos,Element data)
{
	int index = pos - arr->base;
	int mcount = arr->usage - index;
	if(arr->capacity == arr->usage)
	{
		if(arr->capacity)
		{
			arr->capacity*=2;
		}
		else
		{
			arr->capacity = 1;
		}
		arr->base = (Element *)realloc(arr->base,sizeof(Element)*arr->capacity);
	}
	memcpy(arr->base+index+1,arr->base+index,sizeof(Element)*mcount);
	arr->base[index] = data;
	arr->usage++;
}
void Array_SetAt(Array *arr,int index,Element data)
{
	if((index>=0)&&(index<arr->usage))
	{
		arr->base[index] = data;
	}
}
Element Array_GetAt(Array *arr,int index)
{
	if((index>=0)&&(index<arr->usage))
	{
		return arr->base[index];
	}
	return 0;
}
Iterator Array_Begin(Array *arr)
{
	return arr->base;
}
Iterator Array_End(Array *arr)
{
	return arr->base+arr->usage;
}
void Array_Erase(Array *arr,Iterator pos)
{
	int index = pos - arr->base;
	int mcount = arr->usage - index -1;
	memcpy(pos,pos+1,sizeof(Element)*mcount);
	arr->usage--;
}

//Graph.h
#pragma once
#include "Array.h"
typedef const char * Vertex;
typedef struct _Edge Edge;
struct _Edge
{
    Vertex ep1;
    Vertex ep2;
    int weight;
};

typedef struct _Graph Graph;
struct _Graph
{
    Array *vertexs;
    Array *edges;
};

Graph *New_Graph();
void Delete_Graph(Graph *graph);
int Graph_AddVertex(Graph *graph,Vertex pt);
int Graph_AddEdge(Graph *graph,Vertex ep1, Vertex ep2, int weight);
int Graph_ExistVertex(Graph *graph,Vertex pt);
int Graph_ExistEdge(Graph *graph,Vertex ep1, Vertex ep2);
void Graph_View(Graph *graph);
void Graph_ViewVertexs(Graph *graph);
void Graph_ViewEdges(Graph *graph);
void Graph_FindNeighvor(Graph *graph,Vertex ep, Array *neighvor);
int Graph_GetWeight(Graph *graph,Vertex ep1, Vertex ep2);
int Graph_GetVtCnt(Graph *graph);
Vertex Graph_GetFront(Graph *graph);
int Edge_Include(Edge *edge,Vertex pt);

//Graph.c
#include "Graph.h"
#include <malloc.h>
#include <string.h>
#include <stdio.h>
Edge *New_Edge(Vertex ep1, Vertex ep2, int weight)
{
    Edge *edge = 0;
    edge = (Edge *)malloc(sizeof(Edge));
    edge->ep1 = ep1;
    edge->ep2 = ep2;
    edge->weight = weight;
    return edge;
}
Vertex Edge_AnOther(Edge *edge,Vertex pt)
{
    if(strcmp(edge->ep1,pt)==0)
    {
        return edge->ep2;
    }
    if(strcmp(edge->ep2,pt)==0)
    {
        return edge->ep1;
    }
    return "";
}
int Edge_Include(Edge *edge,Vertex pt)
{
    return (strcmp(edge->ep1,pt)==0)||(strcmp(edge->ep2,pt)==0);
}
Graph *New_Graph()
{
    Graph *graph = 0;
    graph = (Graph *)malloc(sizeof(Graph));
    graph->vertexs = New_Array();
    graph->edges = New_Array();
    return graph;
}
void Delete_Graph(Graph *graph)
{
    Iterator seek = 0, end = 0;
    Edge *edge = 0;
    seek = Array_Begin(graph->edges);
    end = Array_End(graph->edges);
    for(seek = seek; seek != end; ++seek)
    {
        edge = (Edge *)(*seek);
        free(edge);
    }
    Delete_Array(graph->vertexs);
    Delete_Array(graph->edges);
    free(graph);
}
int Graph_AddVertex(Graph *graph,Vertex pt)
{
    if(Graph_ExistVertex(graph,pt))
    {
        return 0;
    }
    Array_PushBack(graph->vertexs,(Element)pt);
    return 1;
}
int Graph_AddEdge(Graph *graph,Vertex ep1, Vertex ep2, int weight)
{
    if(Graph_ExistVertex(graph,ep1) && Graph_ExistVertex(graph,ep2))
    {
        Edge *edge = 0;
        if(Graph_ExistEdge(graph,ep1,ep2))
        {
            return 0;
        }
        edge = New_Edge(ep1,ep2,weight);
        Array_PushBack(graph->edges,edge);
        return 1;
    }
    return 0;
}
int Graph_ExistVertex(Graph *graph,Vertex pt)
{
    Iterator seek = 0, end = 0;
    Vertex stored_pt = 0;
    seek = Array_Begin(graph->vertexs);
    end = Array_End(graph->vertexs);
    for(seek = seek; seek != end; ++seek)
    {
        stored_pt = (Vertex)(*seek);
        if(strcmp(stored_pt,pt)==0)
        {
            return 1;
        }
    }
    return 0;
}
int Graph_ExistEdge(Graph *graph,Vertex ep1, Vertex ep2)
{
    Iterator seek = 0, end = 0;
    Edge *stored_eg = 0;
    seek = Array_Begin(graph->edges);
    end = Array_End(graph->edges);
    for(seek = seek; seek != end; ++seek)
    {
        stored_eg = (Edge *)(*seek);
        if(Edge_Include(stored_eg,ep1)&&Edge_Include(stored_eg,ep2))
        {
            return 1;
        }
    }
    return 0;	
}
void Graph_View(Graph *graph)
{
    Graph_ViewVertexs(graph);
    Graph_ViewEdges(graph);
}
void Graph_ViewVertexs(Graph *graph)
{
    Iterator seek = 0, end = 0;
    Vertex pt = 0;
    printf("정점 개수:%d\n",graph->vertexs->usage);
    seek = Array_Begin(graph->vertexs);
    end = Array_End(graph->vertexs);
    for(seek = seek; seek != end; ++seek)
    {
        pt = (Vertex)(*seek);
        printf("%s\n",pt);
    }	
}
void Graph_ViewEdges(Graph *graph)
{
    Iterator seek = 0, end = 0;
    Edge *edge = 0;
    printf("간선 개수:%d\n",graph->edges->usage);
    seek = Array_Begin(graph->edges);
    end = Array_End(graph->edges);
    for(seek = seek; seek != end; ++seek)
    {
        edge = (Edge *)(*seek);
        printf("(%s ,%s):%d\n",edge->ep1,edge->ep2,edge->weight);
    }	
}
void Graph_FindNeighvor(Graph *graph,Vertex ep, Array *neighvor)
{
    Iterator seek = 0, end = 0;
    Edge *edge = 0;
    seek = Array_Begin(graph->edges);
    end = Array_End(graph->edges);
    for(seek = seek; seek != end; ++seek)
    {
        edge = (Edge *)(*seek);
        if(Edge_Include(edge,ep))
        {
            Vertex opt;
            opt = Edge_AnOther(edge,ep);
            Array_PushBack(neighvor,(Element)opt);
        }
    }	
}
int Graph_GetWeight(Graph *graph,Vertex ep1, Vertex ep2)
{
    Iterator seek = 0, end = 0;
    Edge *edge = 0;
    seek = Array_Begin(graph->edges);
    end = Array_End(graph->edges);
    for(seek = seek; seek != end; ++seek)
    {
        edge = (Edge *)(*seek);
        if(Edge_Include(edge,ep1)&&Edge_Include(edge,ep2))
        {
            return edge->weight;
        }
    }	
    return -1;
}
int Graph_GetVtCnt(Graph *graph)
{
    return graph->vertexs->usage;
}
Vertex Graph_GetFront(Graph *graph)
{
    Iterator front = Array_Begin(graph->vertexs);
    return (Vertex)front[0];
}

//Prim.h
#pragma once
#include "Graph.h"
Graph *Prim(Graph *origin);

//Prim.c
#include "Prim.h"
Graph *Prim(Graph *origin);

void SelectVertex(Graph *mstree,Graph *origin);
Graph *Prim(Graph *origin)
{
    Graph *mstree = 0;        
	Vertex vt;
    mstree = New_Graph();
	vt = Graph_GetFront(origin);
    Graph_AddVertex(mstree,vt);
    while(Graph_GetVtCnt(mstree)<Graph_GetVtCnt(origin))
    {
        SelectVertex(mstree,origin);
    }
    return mstree;
}
int IsOnlyOneInclude(Edge *edge, Array *selected);
void SelectVertex(Graph *mstree,Graph *origin)
{
    Array *selected = mstree->vertexs;
    Array *ori_edges = origin->edges;    
    Edge *selectedge=0;

    Iterator seek = 0, end = 0;
    Edge *edge = 0;
    seek = Array_Begin(ori_edges);
    end = Array_End(ori_edges);
    
    for(seek = seek; seek != end; ++seek)
    {
        edge = (Edge *)(*seek);
        if(IsOnlyOneInclude(edge,selected))
        {
            if(selectedge)
            {
                if(selectedge->weight>edge->weight)
                {
                    selectedge = edge;
                }
            }
            else
            {
                selectedge = edge;                
            }            
        }
    }
    Graph_AddVertex(mstree,selectedge->ep1);
    Graph_AddVertex(mstree,selectedge->ep2);
    Graph_AddEdge(mstree,selectedge->ep1,selectedge->ep2,selectedge->weight);
}

int IsOnlyOneInclude(Edge *edge, Array *selected)
{
    Iterator seek = 0, end = 0;
    int cnt = 0;
    Vertex vt;
    seek = Array_Begin(selected);
    end = Array_End(selected);
    for(seek = seek; seek != end; ++seek)
    {
        vt = (Vertex)(*seek);
        if(Edge_Include(edge,vt))
        {
            cnt++;
        }
    }
    return cnt==1;
}

//Program.c
#include "Prim.h"
Graph * InitSimulation();
int main()
{
    Graph *origin = 0;
    Graph *mstree = 0;

    origin = InitSimulation();
    mstree = Prim(origin);
    Graph_View(mstree);

    Delete_Graph(origin);
    Delete_Graph(mstree);
    return 0;
}
Graph * InitSimulation()
{
    Graph *graph = New_Graph();		
    Graph_AddVertex(graph,"A");
    Graph_AddVertex(graph,"B");
    Graph_AddVertex(graph,"C");
    Graph_AddVertex(graph,"D");
    Graph_AddVertex(graph,"E");
    Graph_AddVertex(graph,"F");
    Graph_AddVertex(graph,"G");
    Graph_AddVertex(graph,"H");
    
    Graph_AddEdge(graph,"A","B",5);
    Graph_AddEdge(graph,"A","D",3);
    Graph_AddEdge(graph,"A","E",4);
    Graph_AddEdge(graph,"B","D",3);
    Graph_AddEdge(graph,"B","H",2);
    Graph_AddEdge(graph,"C","D",3);
    Graph_AddEdge(graph,"C","G",4);
    Graph_AddEdge(graph,"D","H",5);
    Graph_AddEdge(graph,"D","E",3);
    Graph_AddEdge(graph,"D","F",3);
    Graph_AddEdge(graph,"E","F",2);
    Graph_AddEdge(graph,"F","G",6);
    Graph_AddEdge(graph,"G","H",3);
    
    Graph_View(graph);	
    return graph;		
}

▷ 실행 결과

정점 개수:8
A
B
C
D
E
F
G
H
간선 개수:13
(A ,B):5
(A ,D):3
(A ,E):4
(B ,D):3
(B ,H):2
(C ,D):3
(C ,G):4
(D ,H):5
(D ,E):3
(D ,F):3
(E ,F):2
(F ,G):6
(G ,H):3
정점 개수:8
A
D
B
H
C
E
F
G
간선 개수:7
(A ,D):3
(B ,D):3
(B ,H):2
(C ,D):3
(D ,E):3
(E ,F):2
(G ,H):3