quick union path compression with two ways nearly O(1) finished

Author: Zu3zz

union-find/05-quick-union-path-compression/main.cpp

@@ -0,0 +1,56 @@
+#include <iostream>
+#include <cassert>
+
+using namespace std;
+
+namespace UF5{
+  class UnionFind{
+  private:
+    int* parent;
+    int* rank;
+    int count;
+  public:
+    UnionFind(int count){
+      parent = new int[count];
+      rank = new int[count];
+      this->count = count;
+    }
+    ~UnionFind(){
+      delete [] parent;
+      delete [] rank;
+    }
+    int find(int q){
+      assert(q >= 0 && q < count);
+      /* path compression
+       * not best solution
+      while(q != parent[q]){
+        parent[q] = parent[parent[q]]
+        q = parent[q];
+      }
+      return q;
+      */
+      // using recursion to get shortest tree
+      if(q != parent[q])
+        parent[q] = find(parent[q]);
+      return parent[q];
+    }
+    bool isConnected(int q, int p){
+      return find(q) == find(p);
+    }
+    void unionElements(int q, int p){
+      int pRoot = find(p);
+      int qRoot = find(q);
+      if(qRoot == pRoot){
+        return;
+      }
+      if(rank[qRoot] < rank[pRoot]){
+        parent[qRoot] = pRoot;
+      } else if(rank[pRoot] < rank[qRoot]){
+        parent[pRoot] = qRoot;
+      } else { // rank[qRoot] == rank[pRoot]
+        parent[pRoot] = qRoot;
+        rank[pRoot] += 1;
+      }
+    }
+  };
+}