Migrating the source files from splex

Makefile

@@ -1,8 +1,7 @@
 .PHONY : docs
 docs :
 	rm -rf docs/build/
-	sphinx-autobuild -b html --watch simplextree/ docs/source/ docs/build/
-
+
 .PHONY : run-checks
 run-checks :
 	isort --check .

include/UnionFind.h

@@ -0,0 +1,75 @@
+//----------------------------------------------------------------------
+//                        Disjoint-set data structure 
+// File:                        union_find.h
+//----------------------------------------------------------------------
+// Copyright (c) 2018 Matt Piekenbrock. All Rights Reserved.
+//
+// Class definition based off of data-structure described here:  
+// https://en.wikipedia.org/wiki/Disjoint-set_data_structure
+
+#ifndef UNIONFIND_H_
+#define UNIONFIND_H_
+
+#include <cstddef>		// size_t
+#include <vector> 		// vector 
+#include <numeric> 		// iota
+#include <algorithm>	// transform
+
+struct UnionFind {
+	using idx_t = std::size_t; 
+	using idx_v = std::vector< size_t >;
+  idx_t size; 
+  mutable idx_v parent, rank;
+
+  UnionFind(const idx_t _size) : size(_size), parent(_size), rank(_size){
+		std::iota(parent.begin(), parent.end(), 0);
+	}
+
+  // Main operations
+	void Union(const idx_t x, const idx_t y){
+		if (x >= size || y >= size){ return; }
+		const idx_t xRoot = Find(x), yRoot = Find(y);
+		if (xRoot == yRoot){ return; }
+		else if (rank[xRoot] > rank[yRoot]) { parent[yRoot] = xRoot; }
+		else if (rank[xRoot] < rank[yRoot]) { parent[xRoot] = yRoot; }
+		else if (rank[xRoot] == rank[yRoot]) {
+			parent[yRoot] = parent[xRoot];
+			rank[xRoot] = rank[xRoot] + 1;
+		}
+	} 
+  idx_t Find(const idx_t x) const {
+		if (x >= size || parent[x] == x){ return x; }
+		else {
+			parent[x] = Find(parent[x]);
+			return parent[x];
+		}
+	}
+  void AddSets(const idx_t n_sets){
+		parent.resize(size + n_sets);
+		std::iota(parent.begin() + size, parent.end(), size); // parent initialized incrementally
+		rank.resize(size + n_sets, 0); // rank all 0 
+		size += n_sets; 
+	}
+
+	// Convenience functions
+  void UnionAll(const idx_v& idx){
+		if (idx.size() <= 1){ return; }
+		const idx_t n_pairs = idx.size()-1;
+		for (idx_t i = 0; i < n_pairs; ++i){ Union(idx[i], idx[i+1]); }
+	}
+  idx_v FindAll(const idx_v& idx){
+		if (idx.size() == 0){ return idx_v(); }
+		idx_v cc = idx_v(idx.size());
+		std::transform(idx.begin(), idx.end(), cc.begin(), [this](const size_t i){
+			return(Find(i));
+		});
+		return(cc);
+	}
+  idx_v ConnectedComponents(){
+		idx_v cc = idx_v(size);
+		for (size_t i = 0; i < size; ++i){ cc[i] = Find(i); }
+		return(cc);
+	}
+}; // class UnionFind
+
+#endif