最小生成树的kruskal算法

自己根据kruakal的算法（核心是贪心算法）描述写了一个最小生成树的代码，

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>

#define INT32 int
#define MAXNUMEDGE 1024
#define PRINTF

typedef struct EDGE_H
{
    INT32 u;
    INT32 v;
    INT32 key;
}EDGE;

//边从0开始计数
EDGE edge[MAXNUMEDGE];  //用来存储所有的边的数据
static INT32 numberofedge;
EDGE *minspanedge;   //生成树时用到的边
INT32 *minspancity;  //使用的边所属于的集合

//交换边
int swapedge(INT32 iedge, INT32 jedge)
{
    if(iedge>= numberofedge||jedge>=numberofedge)
        return 0;

    EDGE tmp;
    tmp.u = edge[iedge].u;
    tmp.v = edge[iedge].v;
    tmp.key = edge[iedge].key;

    edge[iedge].u = edge[jedge].u;
    edge[iedge].v = edge[jedge].v;
    edge[iedge].key = edge[jedge].key;

    edge[jedge].u = tmp.u;
    edge[jedge].v = tmp.v;
    edge[jedge].key = tmp.key;

    return 1;

}

/*
 * 得到两个边的较小边
 * */
INT32 minedge(const int iedge,const int jedge)
{
    int minnumedge;
    minnumedge = edge[iedge].key>edge[jedge].key?jedge:iedge;
    return minnumedge;
}

/*
 * 通过最小堆的方式来每次得到最小边
 * */
void minheapofedge(INT32 count)
{
   int i;
   INT32 minkeynum;
   for(i=((numberofedge-count)>>1)-1; i>=0; i--)
   {
       if(((i>>1)+2)<(numberofedge-count))//右结点存在
       {
           minkeynum = minedge((i>>1)+2,(i>>1)+1);

           if(edge[i].key>edge[minkeynum].key)//做交换
           {
               swapedge(i,minkeynum);
           }
       }
       else//右节点不存在
       {
           if(edge[i].key>edge[(i>>1)+1].key)
           {
               swapedge(i,(i>>1)+1);
           }
       }
   }
}

/*
 * 查找元素是否属于集合,返回集合的头
 * */
INT32 isset(const INT32 ucity)
{
    INT32 tempcity=ucity;
    if(ucity == minspancity[ucity]){}
    else
    {
        while(tempcity != minspancity[tempcity])
        {
            tempcity = minspancity[tempcity];
        }
    }
    printf("isset:ucity:%d,set:%d\n",ucity,tempcity);
    return tempcity;
}

/*
 * 合并两个集合
 * */
void mergeset(INT32 uset,INT32 vset)
{
    if(minspancity[uset]>minspancity[vset])
        minspancity[uset]=minspancity[vset];
    else
        minspancity[vset]=minspancity[uset];
}

/*
 * 最小生成树
 * */
void minspantree()
{

    INT32 i,count=0;
    INT32 ucity,vcity;
    EDGE minedge;
    for(i=0; i<numberofedge; i++)
    {
       minheapofedge(count);
       minedge = edge[0];//得到了最小边 //------------------------------------------(1)
#ifdef PRINTF
printf("minedge:u%d,v%d,key%d\n",minedge.u,minedge.v,minedge.key);
#endif
       ucity = isset(minedge.u);
       vcity = isset(minedge.v);
       if(ucity!=vcity)
       {
           //把两个集合合并
           mergeset(ucity,vcity);

           //把边添加进最小生成树里面
           minspanedge[count] = minedge;
           count++;

       }
       else
       {
           /*
            if(minspancity[ucity]>minspancity[vcity])
                minspancity[vcity] = minspancity[ucity];
            else
                minspancity[ucity] = minspancity[vcity];
                */
       }

       //把选出的边处理了
       swapedge(0,numberofedge-i-1);

    }
}


/*
 * 读取道路的数据
 * */
int readroad()
{
    int ucity,vcity,distance;
    int i;
    for(i=0; i<numberofedge; i++)
    {
        scanf("%d %d %d",&ucity,&vcity,&distance);
        edge[i].u = ucity;
        edge[i].v = vcity;
        edge[i].key = distance;
    }
    return i;

}


int main()
{
    printf("请输入城市个数和城市之间的道路条数\n");
    printf("请输入具体的两个城市和道路名\n");

    int numofcities,cities,i;
    scanf("%d %d",&numofcities,&cities);
    numberofedge = cities;
    minspanedge = (EDGE *)malloc(sizeof(EDGE)*numberofedge);
    bzero(minspanedge,sizeof(minspanedge));
    minspancity = (INT32 *)malloc(sizeof(INT32)*numofcities);

    for(i=0; i<numofcities; i++)
        minspancity[i] = i;

    if(numberofedge != readroad()||numberofedge<numofcities-1)
    {
        printf("readroad read error!\n");
        return ;
    }
  /*
    swapedge(0,1);
    for(i=0; i<numberofedge; i++)
    {
    printf("%d  %d  %d\n",edge[i].u,edge[i].v,edge[i].key);
    }
*/
    minspantree();

    printf("城市  城市  距离\n");
    for(i=0; i<numofcities-1; i++)
        printf("%d  %d  %d\n",minspanedge[i].u,minspanedge[i].v,minspanedge[i].key);



}

在这次写的代码中发现思路上都是正确的，每个函数的代码都是正确的，但是在变量的使用上太不小心了，就是因为变量的错误导致运行的结果出现错误。

结构体是可以直接赋值的，如(1)处。