ds lab 9 task 1

#include<bits/stdc++.h>
using namespace std;
int n,cnt=0;
int tree[2000];
int ar[1000];
void init(int node,int b,int e)
{
    if(b==e)
    {
        tree[node]=ar[b];
        cnt=max(cnt,node);
        return;
    }
    int left=node*2;
    int right=(node*2)+1;
    int mid=(b+e)/2;
    init(left,b,mid);
    init(right,mid+1,e);
    tree[node]=tree[left]+tree[right];
    cnt=max(cnt,node);
}
int query_sum(int node,int b,int e,int i,int j)
{
    if(i>e||j<b)
        return 0;
    if(b>=i&&e<=j)
        return tree[node];
    int left=node*2;
    int right=(node*2)+1;
    int mid=(b+e)/2;
    int p1=query_sum(left,b,mid,i,j);
    int p2=query_sum(right,mid+1,e,i,j);
    return p1+p2;
}
int update(int node,int b,int e,int i,int newVal)
{
    if(i>e||i<b)
        return 0;
    if(b==i&&e==i)
    {
        tree[node]=newVal;
        return 0;
    }
    int left=node*2;
    int right=(node*2)+1;
    int mid=(b+e)/2;
    update(left,b,mid,i,newVal);
    update(right,mid+1,e,i,newVal);
    tree[node]=tree[left]+tree[right];
}
void printtree()
{
    int i;
    cout<<"The Segment Tree Array is : ";
    for(i=1;i<=cnt;i++)
        cout<<tree[i]<<" ";
    cout<<endl;
}
int main()
{
    int i;
    cout<<"Number of elements"<<endl;
    cin>>n;
    for(i=1;i<=n;i++)
        cin>>ar[i];
    init(1,1,n);
    printtree();
    cout<<"Sum of (2..6) : "<<query_sum(1,1,n,2,6)<<endl;
    update(1,1,n,3,43);
    cout<<"After Update"<<endl;
    printtree();
}