算法-并查集-1

public class Element<V> {
    public V value;

    public Element(V value) {
        this.value = value;
    }

    public static class UnionFindSet<V> {
        public Map<V, Element<V>> elementMap;
        public Map<Element<V>, Element<V>> fatherMap;
        public Map<Element<V>, Integer> sizeMap;

        public UnionFindSet(List<V> list) {
            elementMap = new HashMap<>();
            fatherMap = new HashMap<>();
            sizeMap = new HashMap<>();
            if (list != null && !list.isEmpty()) {
                for (V v : list) {
                    Element<V> vElement = new Element<>(v);
                    elementMap.put(v, vElement);
                    fatherMap.put(vElement, vElement);
                    sizeMap.put(vElement, 1);
                }
            }
        }

        public Element<V> findHead(Element<V> element) {
            Stack<Element<V>> stack = new Stack<>();
            while (fatherMap.get(element) != element) {
                stack.push(element);
                element = fatherMap.get(element);
            }
            while (!stack.isEmpty()) {
                fatherMap.put(stack.pop(), element);
            }
            return element;
        }

        public boolean isSameSet(V a, V b) {
            if (elementMap.containsKey(a) && elementMap.containsKey(b)) {
                Element<V> aHead = findHead(elementMap.get(a));
                Element<V> bHead = findHead(elementMap.get(b));
                if (aHead == bHead) {
                    return true;
                }
            }
            return false;

        }

        public void union(V a, V b) {
            if (elementMap.containsKey(a) && elementMap.containsKey(b)) {
                Element<V> aElement = elementMap.get(a);
                Element<V> bElement = elementMap.get(b);
                Element<V> aHead = findHead(aElement);
                Element<V> bHead = findHead(bElement);
                Integer aSize = sizeMap.get(aElement);
                Integer bSize = sizeMap.get(bElement);
                Element<V> big =aSize > bSize ? aHead : bHead;
                Element<V> small = big == aHead ? bHead : aHead;
                fatherMap.put(small,big);
                sizeMap.put(big,aSize+bSize);
                sizeMap.remove(small);
            }
        }
    }
}

并查集结构 可以快速查询是否在同一个集合 

快速集合合并