Create FenwickTree.cpp

Author: Nirav116

Graph/FenwickTree/FenwickTree.cpp

@@ -0,0 +1,66 @@
+#include<bits/stdc++.h>
+
+using namespace  std;
+#define mx 100009
+typedef long long int ll;
+int arr[mx];
+int bit[mx];
+int n,m;
+void update(int index,ll  val)
+{
+    index+=1;
+    while(index<=n)
+    {
+        bit[index]+=val;
+        index += index & (-index);
+
+    }
+
+}
+ll getsum(int index)
+{
+    ll sum=0;
+    index+=1;
+    while(index>0)
+    {
+        //cout<<index<<" "<<bit[index]<<endl;
+        sum+=bit[index];
+        index-=index&(-index);
+    }
+    return sum;
+}
+int main()
+{
+
+    cin>>n>>m;
+    for(int i=0;i<n;i++)
+        cin>>arr[i];
+
+    memset(bit,0,sizeof bit);
+    for(int i=0;i<n;i++)
+    {
+        update(i,arr[i]);
+    }
+    int x,y,t;
+
+
+    while(m--)
+    {
+
+        cin>>t;
+        if(t==1)
+        {
+            cin>>x>>y;
+            ll diff=y-arr[x];
+            update(x,diff);
+            arr[x]=y;
+        }
+        else
+        {
+            cin>>x;
+
+            cout<<getsum(x)<<endl;
+        }
+    }
+    return 0;
+}