union-find算法

public class UF
{
	private int[] id;     //分量id（以触点作为索引）
	private int count;    //分量数量
	public UF(int N)
	{
		//初始化分量数组
		count = N;
		id = new int[N];
		for (int i = 0; i < N; i++)
			id[i] = i;
	}
	public int count()
	{	return count;	}
	public boolean connected(int p,int q)
	{	return find(p) == find(q);	}
	public int find(int p)
	public void union(int p,int q)
	public static void main(String[] args)
	{
		int N = StdIn.readInt();     //读取触点数量
		UF uf = new UF(N);           //初始化N个分量
		while (!StdIn.isEmpty())
		{
			int p = StdIn.readInt();
			int q = StdIn.readInt();  //读取整数对
			if (uf.connected(p, q)) continue;  //已经连通则忽略
			uf.union(p, q);           //归并分量
			StdOut.println(p + " " + q);       //打印连接
		}
		StdOut.println(uf.count() + "components");
	}
}

　　quick-find算法

public int find(int p)
{	return id[p];	}
public void union(int p, int q)
{	//将p和q归并到相同的分量中
	int pID = find(p);
	int qID = find(q);
	//p和q在相同的分量中，不采取行动
	if (pID == qID) return;
	//将p的分量重命名为q的名称
	for (int i = 0; i < id.length; i++)
		if (id[i] == pID) id[i] = qID;
	count--;
}

　　quick-union算法

public int find(int p)
{	//找出分量的名称
	while (p != id[p]) p = id[p];
	return p;
}
public void union(int p, int q)
{	//将p和q的根节点统一
	int pRoot = find(p);
	int qRoot = find(q);
	if (pRoot == qRoot) return;
	id[pRoot] = qRoot;
	count--;
}

　　加权quick-union算法

public class WeightedQuickUnionUF
{
	private int[] id;       //父链接数组（由触电索引）
	private int[] sz;       //（由触电索引的）各个根节点所对应的分量大小
	private int count;      //连通分量的数量
	public WeightedQuickUnionUF(int N)
	{
		count = N;
		id = new int[N];
		for (int i = 0; i < N; i++) id[i] = i;
		sz = new int[N];
		for (int i = 0; i < N; i++) sz[i] = 1;
	}
	public int count()
	{	return count;	}
	public boolean connected(int p, int q)
	{	return find(p) == find(q);	}
	private int find(int p)
	{	//跟随连接找到根节点
		while (p != id[p]) p = id[p];
		return p;
	}
	public void union(int p, int q)
	{
		int i = find(p);
		int j = find(q);
		if (i == j) return;
		// 将小树的根节点连接到大树的根节点上
		if	(sz[i] < sz[j]) { id[i] = j; sz[j] += sz[i]; }
		else				{ id[j] = i; sz[i] += sz[j]; }
		cpunt--;
	}
}

　　

转载于:https://www.cnblogs.com/auhz/p/8987575.html