quick union

Author: hackfengJam

UnionFind/src/Main.java

@@ -0,0 +1,44 @@
+import java.util.Random;
+
+public class Main {
+    private static double testUF(UF uf, int m) {
+        int size = uf.getSize();
+        Random random = new Random();
+
+        long startTime = System.nanoTime();
+
+        // 执行 m 次合并操作
+        for (int i = 0; i < m; i++) {
+            int a = random.nextInt(size);
+            int b = random.nextInt(size);
+            uf.unionElements(a, b);
+        }
+
+        // 执行 m 次查询操作
+        for (int i = 0; i < m; i++) {
+            int a = random.nextInt(size);
+            int b = random.nextInt(size);
+            uf.isConnected(a, b);
+        }
+
+
+        long endTime = System.nanoTime();
+
+        return (endTime - startTime) / 1000000000.0;
+
+    }
+
+    public static void main(String[] args) {
+        int size = 100000;
+        int m = 10000;
+
+
+        UnionFind1 uf1 = new UnionFind1(size);
+        System.out.println("UnionFind1 : " + testUF(uf1, m) + " s");
+
+
+        UnionFind2 uf2 = new UnionFind2(size);
+        System.out.println("UnionFind2 : " + testUF(uf2, m) + " s");
+
+    }
+}

UnionFind/src/UnionFind2.java

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+public class UnionFind2 implements UF {
+
+    private int[] parent;
+
+    public UnionFind2(int size) {
+        parent = new int[size];
+
+        for (int i = 0; i < size; i++) {
+            parent[i] = i;
+        }
+    }
+
+    @Override
+    public int getSize() {
+        return parent.length;
+    }
+
+    // 查找过程，查找元素p对应的集合编号
+    // O(h)复杂度，h为树的高度
+    private int find(int p) {
+
+        if (p < 0 && p >= parent.length) {
+            throw new IllegalArgumentException("p is out of bound");
+        }
+
+        while (p != parent[p]) {
+            p = parent[p];
+        }
+        return p;
+    }
+
+    // 查看元素p和元素q是否所属一个集合
+    @Override
+    public boolean isConnected(int p, int q) {
+        return find(p) == find(q);
+    }
+
+    // 合并元素p和元素q所属的集合
+    // O(h) 复杂度，h为树的高度
+    @Override
+    public void unionElements(int p, int q) {
+        int pRoot = find(p);
+        int qRoot = find(q);
+        if (pRoot == qRoot) {
+            return;
+        }
+        parent[pRoot] = qRoot;
+
+    }
+}