From 4f9bec08ae243e95ef629afa18c45f56f78c5946 Mon Sep 17 00:00:00 2001
From: Vivek Kumar <techfreakology@gmail.com>
Date: Wed, 9 Oct 2019 00:55:20 +0530
Subject: [PATCH] disjoint_sets.cpp: Added Disjoint sets data structure

A disjoint-set data structure is a data structure that keeps track of a set of elements partitioned into a number of disjoint (non-overlapping) subsets. A union-find algorithm is an algorithm that performs two useful operations on such a data structure:
Find: Determine which subset a particular element is in. This can be used for determining if two elements are in the same subset.
Union: Join two subsets into a single subset.
---
 Data Structures/disjoint_sets.cpp | 80 +++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 Data Structures/disjoint_sets.cpp

diff --git a/Data Structures/disjoint_sets.cpp b/Data Structures/disjoint_sets.cpp
new file mode 100644
index 000000000..9f56b364a
--- /dev/null
+++ b/Data Structures/disjoint_sets.cpp	
@@ -0,0 +1,80 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class disjoint_set
+{
+    public:
+    vector<int> ds;
+    disjoint_set(int n)
+    {
+        ds.resize(n + 1);
+        for(int i = 1; i <= n; i++)
+        {
+            make_set(i);
+        }
+    }
+    void make_set(int node);
+    int find_set(int node);
+    void union_sets(int node_a, int node_b);
+    void print_disjoint_sets();
+};
+
+void disjoint_set::make_set(int node)
+{
+    ds[node] = node;
+}
+
+int disjoint_set::find_set(int node)
+{
+    if(ds[node] == node)
+        return node;
+    else
+        return ds[node] = find_set(ds[node]);
+}
+
+void disjoint_set::union_sets(int node_a, int node_b)
+{
+    ds[node_a] = node_b;
+}
+
+void disjoint_set::print_disjoint_sets()
+{
+    map<int, vector<int>> disjoint_sets;
+    for(int i = 1; i <= ds.size(); i++)
+    {
+        disjoint_sets[find_set(ds[i])].push_back(i);
+    }
+    cout << "Disjoint sets are following:\n";
+    int set_number = 1;
+    for(auto it : disjoint_sets)
+    {
+        cout << "Set " << set_number++ << ": ";
+        for(auto jt : it.second)
+        {
+            cout << jt << " ";
+        }
+        cout << "\n";
+    }
+}
+
+int main()
+{
+    int nodes;
+    cin >> nodes;
+    disjoint_set dsu(nodes);
+    int edges;
+    cin >> edges;
+    for(int i = 0; i < edges; i++)
+    {
+        int u,v;
+        cin >> u >> v;
+        int parent_u = dsu.find_set(u);
+        int parent_v = dsu.find_set(v);
+        if(parent_u != parent_v)
+        {
+            dsu.union_sets(parent_u, parent_v);
+        }
+    }
+    dsu.print_disjoint_sets();
+    return 0;
+}