HDU 5253 最小生成树（kruskal）+ 并查集

题目链接

#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
#define N 1000010
using namespace std;
struct node
{
    int a;//端点1
    int b;//端点2
    int num;//权值
};
bool cmp(node x,node y)//按权值升序
{
    return x.num<y.num;
}
int maps[1003][1003];
node edge[N*2];//边数=2mn-m-n<2mn
int father[N];
int r[N];
int finds(int x)
{
    if(father[x]!=x)
    father[x]=finds(father[x]);
    return father[x];
}
void connect(int a,int b)
{
    if(r[a]>r[b])
    father[b]=a;
    else if(r[a]<r[b])
    father[a]=b;
    else
    {
        father[a]=b;
        r[b]++;
    }
}
int main()
{
    int T,cas=1,n,m,ans,id;
    int i,j;
    scanf("%d",&T);
    while(T--)
    {
        int numedge=0;//边数
        ans=0;
        memset(r,0,sizeof(r));
        scanf("%d%d",&n,&m);
        for(i=1;i<=n;i++)
        {
            for(j=1;j<=m;j++)
            scanf("%d",&maps[i][j]);
        }
        for(i=1;i<=n;i++)
        {
            for(j=1;j<=m;j++)
            {
                id=(i-1)*m+j;
                father[id]=id;
                if(i<n)//除最后一行外
                {
                    numedge++;
                    edge[numedge].a=id;
                    edge[numedge].b=i*m+j;
                    edge[numedge].num=abs(maps[i][j]-maps[i+1][j]);
                }
                if(j<m)//除最后一列外
                {
                    numedge++;
                    edge[numedge].a=id;
                    edge[numedge].b=(i-1)*m+j+1;
                    edge[numedge].num=abs(maps[i][j]-maps[i][j+1]);
                }
            }
        }
        sort(edge+1,edge+numedge+1,cmp);//权值排序
        for(i=1;i<=numedge;i++)
        {
            int x=finds(edge[i].a);
            int y=finds(edge[i].b);
            if(x!=y)
            {
                connect(x,y);
                ans+=edge[i].num;
            }
        }
        printf("Case #%d:
%d
",cas++,ans);
    }
    return 0;
}