Kruskal 2015百度之星初赛2 HDOJ 5253 连接的管道

题目传送门

/*
    最小生成树(Kruskal)：以权值为头，带入两个端点，自然的排序;感觉结构体的并查集很好看
    注意：题目老头要的是两个农田的高度差，中文水平不好，题意理解成和平均值的高度差！
*/
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <vector>
#include <queue>
#include <set>
using namespace std;

const int MAXN = 1e3 + 10;
const int MAXM = 1e2 + 10;
const int INF = 0x3f3f3f3f;
int n, m;
int a[MAXN][MAXN];
vector<pair<int, int> > G[MAXM];
struct UF
{
    int rt[MAXN*MAXN];
    void init(void)    {memset (rt, -1, sizeof (rt));}

    int Find(int x)    {return (rt[x] == -1) ? x : rt[x] = Find (rt[x]);}

    void Union(int x, int y)
    {
        x = Find (x);    y = Find (y);
        if (x > y)    rt[y] = x;
        else if (x < y)    rt[x] = y;
    }

    bool same(int x, int y)    {return Find (x) == Find (y);}
}uf;

int Kruskal(void)
{
    uf.init ();
    int ans = 0;
    for    (int i=0; i<=100; ++i)
    {
        for (int j=0; j<G[i].size (); ++j)
        {
            int u = G[i][j].first;    int v = G[i][j].second;
            if (!uf.same (u, v))    {uf.Union (u, v);    ans += i;}
        }
    }

    return ans;
}

int get_id(int i, int j)    {return (i - 1) * m + j;}

int main(void)        //2015百度之星初赛2 HDOJ 5253 连接的管道
{
    int t, cas = 0;    scanf ("%d", &t);
    while (t--)
    {
        scanf ("%d%d", &n, &m);
        for (int i=0; i<=100; ++i)    G[i].clear ();

        for (int i=1; i<=n; ++i)
        {
            for (int j=1; j<=m; ++j)
            {
                scanf ("%d", &a[i][j]);
                if (i > 1)    {G[abs (a[i][j] - a[i-1][j])].push_back (make_pair (get_id (i, j), get_id (i-1, j)));}
                if (j > 1)    {G[abs (a[i][j] - a[i][j-1])].push_back (make_pair (get_id (i, j), get_id (i, j-1)));}
            }
        }

        printf ("Case #%d:
", ++cas);
        printf ("%d
", Kruskal ());
    }

    return 0;
}


/*
2
4  3
9 12 4
7 8 56
32 32 43
21 12 12
2  3
34 56 56
12 23 4
*/