Create alternate_disjoint_set.py

data_structures/disjoint_set/alternate_disjoint_set.py

@@ -0,0 +1,51 @@
+"""
+This code implements a disjoint set using Lists 
+with added heuristics for efficiency
+Union by Rank Heuristic and Path Compression
+"""
+class DisjointSet:
+    def __init__(self, set_count):
+        """
+        Initialize with the number of items in each set
+        and with rank = 1 for each set
+        """
+        self.set_count = set_count
+        self.max_set = max(set_count)
+        num_sets = len(set_count)
+        self.ranks = [1] * num_sets
+        self.parents = list(range(num_sets))
+
+    def merge(self, src, dst):
+        """
+        union by rank
+        """
+        src_parent = self.get_parent(src)
+        dst_parent = self.get_parent(dst)
+
+        if src_parent == dst_parent:
+            return False
+
+        if self.ranks[dst_parent] >= self.ranks[src_parent]:
+            self.set_count[dst_parent] += self.set_count[src_parent]
+            self.set_count[src_parent] = 0
+            self.parents[src_parent] = dst_parent
+            if self.ranks[dst_parent] == self.ranks[src_parent]:
+                self.ranks[dst_parent] += 1
+            joined_set_size = self.set_count[dst_parent]
+        else:
+            self.set_count[src_parent] += self.set_count[dst_parent]
+            self.set_count[dst_parent] = 0
+            self.parents[dst_parent] = src_parent
+            joined_set_size = self.set_count[src_parent]
+
+        self.max_set = max(self.max_set, joined_set_size)
+        return True
+
+    def get_parent(self, set):
+        """
+        Find Parent and Compress Path
+        """
+        if self.parents[set] == set:
+            return set
+        self.parents[set] = self.get_parent(self.parents[set])
+        return self.parents[set]