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71 lines
1.6 KiB
71 lines
1.6 KiB
package class14;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Stack;
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public class Code05_UnionFind {
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public static class Node<V> {
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V value;
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public Node(V v) {
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value = v;
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}
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}
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public static class UnionFind<V> {
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public HashMap<V, Node<V>> nodes;
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public HashMap<Node<V>, Node<V>> parents;
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public HashMap<Node<V>, Integer> sizeMap;
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public UnionFind(List<V> values) {
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nodes = new HashMap<>();
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parents = new HashMap<>();
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sizeMap = new HashMap<>();
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for (V cur : values) {
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Node<V> node = new Node<>(cur);
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nodes.put(cur, node);
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parents.put(node, node);
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sizeMap.put(node, 1);
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}
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}
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// 给你一个节点，请你往上到不能再往上，把代表返回
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public Node<V> findFather(Node<V> cur) {
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Stack<Node<V>> path = new Stack<>();
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while (cur != parents.get(cur)) {
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path.push(cur);
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cur = parents.get(cur);
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}
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while (!path.isEmpty()) {
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parents.put(path.pop(), cur);
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}
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return cur;
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}
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public boolean isSameSet(V a, V b) {
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return findFather(nodes.get(a)) == findFather(nodes.get(b));
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}
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public void union(V a, V b) {
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Node<V> aHead = findFather(nodes.get(a));
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Node<V> bHead = findFather(nodes.get(b));
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if (aHead != bHead) {
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int aSetSize = sizeMap.get(aHead);
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int bSetSize = sizeMap.get(bHead);
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Node<V> big = aSetSize >= bSetSize ? aHead : bHead;
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Node<V> small = big == aHead ? bHead : aHead;
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parents.put(small, big);
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sizeMap.put(big, aSetSize + bSetSize);
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sizeMap.remove(small);
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}
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}
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public int sets() {
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return sizeMap.size();
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}
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}
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}
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