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c++/Others/DisjSets.cpp - Efficient implementation of disjoint sets algorithm.cpp

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+DisjSets.cpp - Efficient implementation of disjoint sets algorithm
+
+#include "DisjSets.h"
+
+/**
+ * Construct the disjoint sets object.
+ * numElements is the initial number of disjoint sets.
+ */
+DisjSets::DisjSets( int numElements ) : s( numElements )
+{
+    for( int i = 0; i < s.size( ); i++ )
+        s[ i ] = -1;
+}
+
+/**
+ * Union two disjoint sets.
+ * For simplicity, we assume root1 and root2 are distinct
+ * and represent set names.
+ * root1 is the root of set 1.
+ * root2 is the root of set 2.
+ */
+void DisjSets::unionSets( int root1, int root2 )
+{
+    if( s[ root2 ] < s[ root1 ] )  // root2 is deeper
+        s[ root1 ] = root2;        // Make root2 new root
+    else
+    {
+        if( s[ root1 ] == s[ root2 ] )
+            s[ root1 ]--;          // Update height if same
+        s[ root2 ] = root1;        // Make root1 new root
+    }
+}
+
+
+/**
+ * Perform a find.
+ * Error checks omitted again for simplicity.
+ * Return the set containing x.
+ */
+int DisjSets::find( int x ) const
+{
+    if( s[ x ] < 0 )
+        return x;
+    else
+        return find( s[ x ] );
+}
+
+
+/**
+ * Perform a find with path compression.
+ * Error checks omitted again for simplicity.
+ * Return the set containing x.
+ */
+int DisjSets::find( int x )
+{
+    if( s[ x ] < 0 )
+        return x;
+    else
+        return s[ x ] = find( s[ x ] );
+}
+