diff --git a/FenwickTree.cpp b/FenwickTree.cpp
new file mode 100644
index 0000000..a035497
--- /dev/null
+++ b/FenwickTree.cpp
@@ -0,0 +1,48 @@
+#include <iostream>
+#include <vector>
+
+template <typename T>
+class FenwickTree {
+	private:
+		int n;
+		std::vector<T> bit;
+	public:
+		FenwickTree(int n) {
+			this -> n = n;
+			bit = std::vector<T>(n+1);
+		}
+
+		void update(int x, T delta) {
+			for(; x <= n; x += x & -x) {
+				bit[x] += delta;
+			}
+		}
+
+		T query(int x) {
+			T res = 0;
+			for(; x > 0; x -= x & -x) {
+				res += bit[x];
+			}
+			return res;
+		}
+
+		T query_range(int l, int r) {
+			return query(r) - query(l-1);
+		}
+};
+
+int main() {
+    // creating FenwickTree object for index from 1 to 10 and type integers;
+    FenwickTree<int> ft(10);
+    
+    //updates
+    ft.update(3, 5);
+    ft.update(4, 1);
+    ft.update(7, 2);
+    
+    //query in range
+    std::cout << ft.query_range(3, 7) <<'\n';
+    std::cout << ft.query_range(4, 6) <<'\n';
+    
+    return 0;
+}
diff --git a/Sorting Algos/CountSort.cpp b/Sorting Algos/CountSort.cpp
deleted file mode 100644
index 364f8bb..0000000
--- a/Sorting Algos/CountSort.cpp	
+++ /dev/null
@@ -1,62 +0,0 @@
-#include<bits/stdc++.h>
-using namespace std;
-void countingSort(int *a,int n,int range)
-{
-    int *freq=new int[range];
-    int *output=new int[n];
-    memset(freq,0,sizeof(freq[0])*range);
-    /*cout<<"Range of elements entered "<<range<<endl;
-    cout<<"\nFrequency Array Initially:\n";
-    for(int i=0;i<range;i++){
-        cout<<freq[i]<<" ";
-    }
-    cout<<"\n";*/
-    for(int i=0;i<n;i++){
-        freq[a[i]]++;
-    }
-    /*cout<<"\nFrequency Array :\n";
-    for(int i=0;i<range;i++){
-        cout<<freq[i]<<" ";
-    }
-    cout<<"\n";*/
-
-    for(int i=1;i<range;i++){
-        freq[i]+=freq[i-1];
-    }
-    /*cout<<"\nUPDATED Frequency Array :\n";
-    for(int i=0;i<range;i++){
-        cout<<freq[i]<<" ";
-    }
-    cout<<"\n";*/
-    for(int i=n-1;i>=0;i--){
-        freq[a[i]]--;
-        output[freq[a[i]]]=a[i];
-    }
-    for(int i=0;i<n;i++){
-        a[i]=output[i];
-    }
-}
-int main()
-{
-    int n,s,e;
-    cout<<"Enter Range you want to Sort StartElement,EndElement\n";
-    cin>>s>>e;
-    n=abs(e-s+1);
-    int *a=new int[n];
-
-    for(int i=0;i<n;i++){
-        cin>>a[i];
-    }
-    //cout<<"No of elements entered "<<n<<endl;
-    //cout<<"Range of elements entered "<<e<<endl;
-    cout<<"\nBefore Sorting :\n";
-    for(int i=0;i<n;i++){
-        cout<<a[i]<<" ";
-    }
-    countingSort(a,n,e+1);
-    cout<<"\nAfter Sorting :\n";
-    for(int i=0;i<n;i++){
-        cout<<a[i]<<" ";
-    }
-    return 0;
-}
diff --git a/Sorting Algos/countsort.cpp b/Sorting Algos/countsort.cpp
index 7b1b66e..dd8474e 100644
--- a/Sorting Algos/countsort.cpp	
+++ b/Sorting Algos/countsort.cpp	
@@ -1,51 +1,62 @@
-#include<iostream>
-#include<string>
-#define n 200
-
+#include<bits/stdc++.h>
 using namespace std;
+void countingSort(int *a,int n,int range)
+{
+    int *freq=new int[range];
+    int *output=new int[n];
+    memset(freq,0,sizeof(freq[0])*range);
+    /*cout<<"Range of elements entered "<<range<<endl;
+    cout<<"\nFrequency Array Initially:\n";
+    for(int i=0;i<range;i++){
+        cout<<freq[i]<<" ";
+    }
+    cout<<"\n";*/
+    for(int i=0;i<n;i++){
+        freq[a[i]]++;
+    }
+    /*cout<<"\nFrequency Array :\n";
+    for(int i=0;i<range;i++){
+        cout<<freq[i]<<" ";
+    }
+    cout<<"\n";*/
 
-void count_sort(int ch[],int num){
-	int arr[n];
-	int temp,i=0;
-	for(i=0;i<n;i++){
-		arr[i]=0;
-	}	
-	
-	for(i=0;i<num;i++){
-		temp=ch[i];
-		arr[temp]++;
-	}	
-	
-	for(i=1;i<n;i++){
-		arr[i]+=arr[i-1];
-	}	
-	for(i=n-1;i>=0;i--){
-		arr[i]=arr[i-1];
-	}
-	
-	int outputarr[num];
-	for(i=0;i<num;i++ ){
-		temp=ch[i];
-		outputarr[arr[temp]]=temp;
-		arr[temp]++;
-	}
-	for(i=0;i<num;i++){
-		ch[i]=outputarr[i];	
-	}
-	
+    for(int i=1;i<range;i++){
+        freq[i]+=freq[i-1];
+    }
+    /*cout<<"\nUPDATED Frequency Array :\n";
+    for(int i=0;i<range;i++){
+        cout<<freq[i]<<" ";
+    }
+    cout<<"\n";*/
+    for(int i=n-1;i>=0;i--){
+        freq[a[i]]--;
+        output[freq[a[i]]]=a[i];
+    }
+    for(int i=0;i<n;i++){
+        a[i]=output[i];
+    }
 }
+int main()
+{
+    int n,s,e;
+    cout<<"Enter Range you want to Sort StartElement,EndElement\n";
+    cin>>s>>e;
+    n=abs(e-s+1);
+    int *a=new int[n];
 
-int main(){
-	cout<<"Input format :  Number of elements of array\n                The elements\n";
-	int k,i=0;
-	scanf("%d",&k);
-	int a[k];
-	for(i=0;i<k;i++){
-		cin>>a[i];
-	}
-	count_sort(a,k);
-	for(i=0;i<k;i++){
-		cout<<a[i]<<" ";
-	}
-	return 0;
+    for(int i=0;i<n;i++){
+        cin>>a[i];
+    }
+    //cout<<"No of elements entered "<<n<<endl;
+    //cout<<"Range of elements entered "<<e<<endl;
+    cout<<"\nBefore Sorting :\n";
+    for(int i=0;i<n;i++){
+        cout<<a[i]<<" ";
+    }
+    countingSort(a,n,e+1);
+    cout<<"\nAfter Sorting :\n";
+    for(int i=0;i<n;i++){
+        cout<<a[i]<<" ";
+    }
+    return 0;
 }