From 3f87fcc4b67ef0ca69eb8c8bc536e8a51108ac32 Mon Sep 17 00:00:00 2001
From: coderanant <coderanant@gmail.com>
Date: Thu, 21 May 2020 23:29:52 +0530
Subject: [PATCH 1/3] feat: add algorithm to check number of components with
 the help of Union Find Structure

---
 graph/connected_components_with_dsu.cpp | 53 +++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 graph/connected_components_with_dsu.cpp

diff --git a/graph/connected_components_with_dsu.cpp b/graph/connected_components_with_dsu.cpp
new file mode 100644
index 000000000..f06f1beb9
--- /dev/null
+++ b/graph/connected_components_with_dsu.cpp
@@ -0,0 +1,53 @@
+#include <iostream>
+#include <vector>
+#include <set>
+
+int N;  // denotes number of nodes;
+int parent[1000001];
+int siz[1000001];
+void make_set() {  // function the initialize every node as it's own parent
+    for (int i = 1; i <= N; i++) {
+        parent[i] = i;
+        siz[i] = 1;
+    }
+}
+// To find the component where following node belongs to
+int find_set(int v) {
+    if (v == parent[v])
+        return v;
+    return parent[v] = find_set(parent[v]);
+}
+
+void union_sets(int a, int b) {  // To join 2 components to belong to one
+    a = find_set(a);
+    b = find_set(b);
+    if (a != b) {
+        if (siz[a] < siz[b])
+            std::swap(a, b);
+        parent[b] = a;
+        siz[a] += siz[b];
+    }
+}
+
+int no_of_connected_components() {  // To find total no of connected components
+    std::set<int> temp;  // temp set to count number of connected components
+    for (int i = 1; i <= N; i++)
+        temp.insert(find_set(i));
+    return temp.size();
+}
+
+// All critical/corner cases have been taken care of.
+// Input your required values: (not hardcoded)
+int32_t main() {
+    std::cin >> N;
+    make_set();
+    int edges;
+    std::cin >> edges;  // no of edges in the graph
+    while (edges--) {
+        int node_a, node_b;
+        std::cin >> node_a >> node_b;
+        union_sets(node_a, node_b);
+    }
+    std::cout << no_of_connected_components() << std::endl;
+    return 0;
+}

From 19be84cf588944f1a5b6755b0cc0b6764c08323d Mon Sep 17 00:00:00 2001
From: coderanant <coderanant@gmail.com>
Date: Fri, 22 May 2020 00:49:03 +0530
Subject: [PATCH 2/3] fix bug

---
 graph/connected_components_with_dsu.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/graph/connected_components_with_dsu.cpp b/graph/connected_components_with_dsu.cpp
index f06f1beb9..d8d0b011b 100644
--- a/graph/connected_components_with_dsu.cpp
+++ b/graph/connected_components_with_dsu.cpp
@@ -38,7 +38,7 @@ int no_of_connected_components() {  // To find total no of connected components
 
 // All critical/corner cases have been taken care of.
 // Input your required values: (not hardcoded)
-int32_t main() {
+int main() {
     std::cin >> N;
     make_set();
     int edges;

From d3b60e0de80b288913d9d059e9a0aed38910cb92 Mon Sep 17 00:00:00 2001
From: coderanant <coderanant@gmail.com>
Date: Fri, 22 May 2020 01:06:40 +0530
Subject: [PATCH 3/3] fix: dynamically allocate all arrays

---
 graph/connected_components_with_dsu.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/graph/connected_components_with_dsu.cpp b/graph/connected_components_with_dsu.cpp
index d8d0b011b..2c5c6dab5 100644
--- a/graph/connected_components_with_dsu.cpp
+++ b/graph/connected_components_with_dsu.cpp
@@ -3,8 +3,8 @@
 #include <set>
 
 int N;  // denotes number of nodes;
-int parent[1000001];
-int siz[1000001];
+std::vector<int> parent;
+std::vector<int> siz;
 void make_set() {  // function the initialize every node as it's own parent
     for (int i = 1; i <= N; i++) {
         parent[i] = i;
@@ -40,6 +40,8 @@ int no_of_connected_components() {  // To find total no of connected components
 // Input your required values: (not hardcoded)
 int main() {
     std::cin >> N;
+    parent.resize(N + 1);
+    siz.resize(N + 1);
     make_set();
     int edges;
     std::cin >> edges;  // no of edges in the graph