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Code05_UnionFind.java
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package class14;
import java.util.HashMap;
import java.util.List;
import java.util.Stack;
// 课上讲的并查集实现
// 请务必看补充的Code06_UnionFind
// 那是数组实现的并查集，并且有测试链接
// 可以直接通过
// 这个文件的并查集是用map实现的
// 但是笔试或者平时用的并查集一律用数组实现
// 所以Code06_UnionFind更具实战意义
// 一定要看！
public class Code05_UnionFind {
// 课上讲的时候
// 包了一层
// 其实不用包一层哦
public static class UnionFind<V> {
public HashMap<V, V> father;
public HashMap<V, Integer> size;
public UnionFind(List<V> values) {
father = new HashMap<>();
size = new HashMap<>();
for (V cur : values) {
father.put(cur, cur);
size.put(cur, 1);
}
}
// 给你一个节点，请你往上到不能再往上，把代表返回
public V findFather(V cur) {
Stack<V> path = new Stack<>();
while (cur != father.get(cur)) {
path.push(cur);
cur = father.get(cur);
}
while (!path.isEmpty()) {
father.put(path.pop(), cur);
}
return cur;
}
public boolean isSameSet(V a, V b) {
return findFather(a) == findFather(b);
}
public void union(V a, V b) {
V aFather = findFather(a);
V bFather = findFather(b);
if (aFather != bFather) {
int aSize = size.get(aFather);
int bSize = size.get(bFather);
if (aSize >= bSize) {
father.put(bFather, aFather);
size.put(aFather, aSize + bSize);
size.remove(bFather);
} else {
father.put(aFather, bFather);
size.put(bFather, aSize + bSize);
size.remove(aFather);
}
}
}
public int sets() {
return size.size();
}
}
}