二维并查集

http://coding.fzu.edu.cn/problem/1191

题意：有一个M行N列的点阵，相邻两点可以相连。一条纵向的连线花费一个单位，一条横向的连线花费两个单位。某些点之间已经有连线了，试问至少还需要花费多少个单位才能使所有的点全部连通。

解法：先合并列在把第一行合并

关键：把行号和列号哈希

/*************************************************************************
    > File Name: a.cpp
    > Author: QWX
    > Mail: 
    > Created Time: 2018/11/24 14:24:14
 ************************************************************************/


//{{{ #include
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<cmath>
#include<queue>
#include<map>
#include<set>
#include<string>
#include<cstring>
#include<complex>
#include<cassert>
//#include<bits/stdc++.h>
#define vi vector<int>
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define pw(x) (1ll << (x))
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()
#define rep(i,l,r) for(int i=(l);i<(r);i++)
#define per(i,r,l) for(int i=(r);i>=(l);i--)
#define FOR(i,l,r) for(int i=(l);i<=(r);i++)
#define cl(a,b) memset(a,b,sizeof(a))
#define fastio ios::sync_with_stdio(false);cin.tie(0);
#define lson l , mid , ls
#define rson mid + 1 , r , rs
#define INF 0x3f3f3f3f
#define LINF 0x3f3f3f3f3f3f3f3f
#define ll long long
#define ull unsigned long long
#define dd(x) cout << #x << " = " << (x) << "," 
#define de(x) cout << #x << " = " << (x) << "
" 
#define endl "
"
using namespace std;
//}}}

int n,m;
const int N=1e6+7;
int f[N];
int ans;
int F(int x){return f[x]==x?x:f[x]=F(f[x]);}
void U(int a,int b){int x=F(a),y=F(b);if(x!=y)f[x]=y,ans+=(abs(a-b)==1?2:1);}
inline int id(int r,int c){return (r-1)*m+c;}

int main()
{
    cin>>n>>m;
    FOR(i,1,n*m)f[i]=i;
    int a,b,c,d;
    while(cin>>a>>b>>c>>d)U(id(a,b),id(c,d));
    ans=0;
    FOR(j,1,m)rep(i,1,n)U(id(i,j),id(i+1,j));
//    de(ans);
    rep(j,1,m)U(id(1,j),id(1,j+1));
    cout<<ans<<endl;
    return 0;
}