Rewrite Disjoint Set Union

Author: manosriram

Disjoint-Sets/Compressed.cpp

@@ -0,0 +1,55 @@
+#include <iostream>
+using namespace std;
+static int parent[264], sz[264], rnk[264];
+
+// Create a new set.
+void make_set(int vertex) {
+ parent[vertex] = vertex;
+ sz[vertex] = 1;
+ rnk[vertex] = 0;
+}
+
+// O(logN) time.
+int find_set(int vertex) {
+ if (vertex == parent[vertex]) return vertex;
+
+ return parent[vertex] = find_set(parent[vertex]);
+}
+
+// Union By Size.
+void union_sets_by_sz(int set_a, int set_b) {
+ set_a = find_set(set_a);
+ set_b = find_set(set_b);
+ if (set_a != set_b) {
+ if (sz[set_a] < sz[set_b]) swap(set_a, set_b);
+
+ parent[set_b] = set_a;
+ sz[set_a] += sz[set_b];
+ }
+}
+
+// Union By Rank.
+void union_sets_by_rank(int set_a, int set_b) {
+ set_a = find_set(set_a);
+ set_b = find_set(set_b);
+ if (set_a != set_b) {
+ if (rnk[set_a] < rnk[set_b]) swap(set_a, set_b);
+ 
+ parent[set_b] = set_a;
+ if (rnk[set_a] == rnk[set_b]) ++rnk[set_a];
+ }
+}
+
+int main() {
+ // Create 3 different sets.
+ make_set(1);
+ make_set(2);
+ make_set(3);
+
+ // Union Operation bw 1 and 2.
+ union_sets_by_sz(1, 2);
+ union_sets_by_rank(2, 3);
+
+ cout << find_set(3); // 1
+}
+

Disjoint-Sets/Naive.cpp

@@ -0,0 +1,33 @@
+#include <iostream>
+using namespace std;
+static int parent[264];
+
+void make_set(int vertex) {
+ parent[vertex] = vertex;
+}
+
+// O(n) time.
+int find_set(int vertex) {
+ if (vertex == parent[vertex]) return vertex;
+
+ return find_set(parent[vertex]);
+}
+
+void union_sets(int set_a, int set_b) {
+ set_a = find_set(set_a);
+ set_b = find_set(set_b);
+ if (set_a != set_b)
+ parent[set_b] = set_a;
+}
+
+int main() {
+ // Create 3 different sets.
+ make_set(1);
+ make_set(2);
+ make_set(3);
+
+ // Union Operation bw 1 and 2.
+ union_sets(1, 2);
+
+ cout << find_set(2); // 1
+}