diff --git a/graphs/count_diconnected_components.cpp b/graphs/count_diconnected_components.cpp
new file mode 100644
index 00000000..0ee61601
--- /dev/null
+++ b/graphs/count_diconnected_components.cpp
@@ -0,0 +1,69 @@
+#include<iostream> 
+#include<list> 
+using namespace std; 
+
+int count=1;
+// Graph class represents a directed graph 
+// using adjacency list representation 
+class Graph 
+{ 
+    int V;
+    list<int> *adj; 
+    void DFSUtil(int v, bool visited[]); 
+public: 
+    Graph(int V); 
+    void addEdge(int v, int w);  
+    void DFS(int v); 
+}; 
+  
+Graph::Graph(int V) 
+{ 
+    this->V = V; 
+    adj = new list<int>[V]; 
+} 
+  
+void Graph::addEdge(int v, int w) 
+{ 
+    adj[v].push_back(w); // Add w to v’s list. 
+} 
+  
+void Graph::DFSUtil(int v, bool visited[]) 
+{ 
+    visited[v] = true;
+    list<int>::iterator i; 
+    for (i = adj[v].begin(); i != adj[v].end(); ++i) 
+        if (!visited[*i]) 
+            DFSUtil(*i, visited); 
+} 
+void Graph::DFS(int v) 
+{  
+    bool *visited = new bool[V]; 
+    for (int i = 0; i < V; i++) 
+        visited[i] = false;
+    DFSUtil(v, visited);
+    for (int i = 0; i < V; i++) 
+        if(visited[i] == false)
+        {
+            count++;
+            DFSUtil(i, visited);
+        }
+} 
+  
+int main() 
+{ 
+    Graph g(9); 
+    g.addEdge(0, 1); 
+    g.addEdge(0, 2); 
+    g.addEdge(1, 2); 
+    g.addEdge(2, 0); 
+    g.addEdge(2, 3); 
+    g.addEdge(3, 3);
+    g.addEdge(4, 5);
+    g.addEdge(6, 7);
+    g.addEdge(6, 8);
+    
+    g.DFS(2);
+    cout << "Number of disconnected components in the given graph is : " <<count;; 
+ 
+    return 0; 
+}
diff --git a/math/modular_exponentiation.cpp b/math/modular_exponentiation.cpp
new file mode 100644
index 00000000..5acf9a30
--- /dev/null
+++ b/math/modular_exponentiation.cpp
@@ -0,0 +1,35 @@
+// modular exponentiation implemented in C++
+//Author : Rituparno Biswas
+
+//Given three numbers x, y and p, compute (power(x,y)) % p. where power(a,b) calculates a to power of b 
+
+
+#include<bits/stdc++.h>
+using namespace std;
+
+typedef long long int ll;
+
+ll power(ll x, ll y, ll p)
+{
+	if(x==0)
+		return 0;
+	if(y==0)
+		return 1;
+	if (y%2==0)
+	{
+		ll g=power(x,y/2,p);
+		return (g*g)%p;
+	}
+	else
+	{
+		ll g=power(x,y/2,p);
+		return (x*(g*g)%p)%p;
+	}
+}
+
+int main() 
+{ 
+   ll x = 2,y = 5, p = 13; 
+   printf("Power is %lld", power(x, y, p)); 
+   return 0; 
+} 
\ No newline at end of file
diff --git a/sorting/selection_sort.cpp b/sorting/selection_sort.cpp
new file mode 100644
index 00000000..0ba110d0
--- /dev/null
+++ b/sorting/selection_sort.cpp
@@ -0,0 +1,49 @@
+// C++ implementation of selection sort
+//
+// Author: Rituparno Biswas
+
+#include <iostream>
+
+// Swap elements
+void swap(int *x, int *y)
+{
+	int temp = *x;
+	*x = *y;
+	*y = temp;
+}
+
+// Implement selection sort
+void selectionSort(int arr[], int n)
+{
+   int i, j, min_id;
+   for (i = 0; i < n-1; i++)
+   {
+   		min_id=i;
+   		for (j = i+1; j < n; j++)
+   			if (arr[min_id] > arr[j])
+   				min_id=j;
+   			swap(&arr[i], &arr[min_id]);
+   	}
+}
+
+// Function to print elements
+void printArray(int arr[], int size)
+{
+	int i;
+	for (i=0; i < size; i++)
+		printf("%d ", arr[i]);
+	printf("\n");
+}
+
+// test
+int main()
+{
+	int arr[] = {46, 24, 33, 10, 2, 81, 50};
+	int n = sizeof(arr)/sizeof(arr[0]);
+	printf("Unsorted array: \n");
+	printArray(arr, n);
+	selectionSort(arr, n);
+  	printf("Sorted array: \n");
+	printArray(arr, n);
+  return 0;
+}