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UnionFind6.java
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UnionFind6.java
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/**
* 并查集
* 第六个版本,路径压缩优化,数组实现
*
* @author ronglexie
* @version 2018/9/1
*/
public class UnionFind6 implements UnionFind{
private int[] parent;//存储当前位置元素的根节点
private int[] rank;//表示以当前元素为根节点的高度
public UnionFind6(int size) {
parent = new int[size];
rank = new int[size];
for (int i = 0; i < size; i++) {
parent[i] = i;
rank[i] = 1;
}
}
@Override
public int getSize() {
return parent.length;
}
/**
* 查找元素p所对应的根节点
*
* @param p
* @return int
* @author ronglexie
* @version 2018/9/1
*/
private int find(int p){
if(p < 0 || p > parent.length){
throw new IllegalArgumentException("p is out of bound.");
}
//递归路径压缩
if (p != parent[p]){
parent[p] = find(parent[p]);
}
return parent[p];
}
@Override
public boolean isConnected(int p, int q) {
return find(p) == find(q);
}
@Override
public void unionElements(int p, int q) {
int pRoot = find(p);
int qRoot = find(q);
if (pRoot == qRoot){
return;
}
//根据以当前元素为根节点的高度来合并
//将以当前元素为根节点的高度低的合并到高的集合上面
if(rank[pRoot] < rank[qRoot]){
parent[pRoot] = qRoot;
}else if(rank[pRoot] > rank[qRoot]) {
parent[qRoot] = pRoot;
}else {
parent[pRoot] = qRoot;
rank[qRoot] += 1;
}
}
}