[UFDS] Add UFDS lib and client in Java

DSLib/Client/UFDS/UfdsClient.java

@@ -0,0 +1,13 @@
+package UFDS;
+
+public class UfdsClient {
+    public static void main(String[] args) {
+        Ufds ufds = new Ufds(10);
+        ufds.unionSet(1, 8);
+        ufds.unionSet(8, 9);
+        ufds.unionSet(8, 3);
+
+        System.out.printf("is same set (1, 9): %b\n", ufds.isSameSet(1, 9));
+        System.out.printf("is same set (1, 4): %b\n", ufds.isSameSet(1, 4));
+    }
+}

DSLib/Lib/UFDS/Ufds.java

@@ -0,0 +1,47 @@
+package UFDS;
+
+public class Ufds {
+    public Ufds(int numNodes) {
+        mNumNodes = numNodes;
+        mRank = new int[mNumNodes];
+        mParentIndex = new int[mNumNodes];
+
+        for (int i = 0; i < mNumNodes; i++) {
+            mParentIndex[i] = i;
+        }
+    }
+
+    public int findSet(int i) {
+        if (mParentIndex[i] == i) {
+            return i;
+        }
+
+        mParentIndex[i] = findSet(mParentIndex[i]);
+        return mParentIndex[i];
+    }
+
+    public boolean isSameSet(int i, int j) {
+        return findSet(i) == findSet(j);
+    }
+
+    public void unionSet(int i, int j) {
+        if (isSameSet(i, j)) {
+            return;
+        }
+
+        int iParent = findSet(i);
+        int jParent = findSet(j);
+        if (mRank[iParent] > mRank[jParent]) {
+            mParentIndex[jParent] = iParent;
+        } else {
+            mParentIndex[iParent] = jParent;
+            if (mRank[iParent] == mRank[jParent]) {
+                ++mRank[jParent];
+            }
+        }
+    }
+
+    private final int mNumNodes;
+    private int[] mParentIndex;
+    private int[] mRank;
+}