Create create_segment_tree.cpp

This is the code for segment tree creation
Please accept the PR for hacktoberfest2022

C++/create_segment_tree.cpp

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+/*
+segment tree
+You have given an array A of n elements. Your task is to process q queries of the following types.
+1 i x : Update the value at position i to x.
+2 i j : Print the sum of values in the range [i, j].
+*/
+
+#include<bits/stdc++.h>
+using namespace std; 
+typedef long long int ll; //g++ ll.cpp -o ll.exe
+typedef long double ld; 
+typedef pair<ll,ll> iii; //all elements to 0
+const ll mod =1e9+7;
+
+
+
+struct node
+{
+ ll x;
+
+};
+
+
+vector<node> g;
+vector<ll> ar;
+
+node merge(node a,node b)
+{
+ node temp;
+ temp.x=a.x+b.x;
+ return temp;
+}
+
+void build(ll index,ll l,ll r)
+{
+
+ if(l==r)
+ {
+ node tt;
+ tt.x=ar[l];
+ g[index]=tt;
+ return;
+ }
+
+ ll mid;
+ mid=(l+r)/2;
+ build(2*index,l,mid);
+ build(2*index+1,mid+1,r);
+ g[index]=merge(g[2*index],g[2*index+1]);
+}
+
+void update(ll index,ll l,ll r,ll pos,ll value)
+{
+
+ if((pos<l)|| (pos>r))
+ return; 
+
+
+ if(l==r)
+ {
+ //cout<<index<<endl;
+ node tt;
+ tt.x=value;
+ g[index]=tt;
+ ar[l]=value;
+ return;
+ }
+
+ ll mid;
+ mid=(l+r)/2;
+ update(2*index,l,mid,pos,value);
+ update(2*index+1,mid+1,r,pos,value);
+ g[index]=merge(g[2*index],g[2*index+1]);
+
+
+}
+
+
+ node query(ll index,ll l,ll r,ll lq,ll rq)
+ {
+ node ans;
+ ans.x=0;
+
+ if(lq> r || rq<l)
+ return ans;
+
+ if(lq<=l && rq>=r)
+ return(g[index]);
+
+ ll mid=(l+r)/2;
+ ans=merge(query(2*index,l,mid,lq,rq),query(2*index+1,mid+1,r,lq,rq));
+
+ return(ans);
+
+
+
+ }
+
+
+int main()
+{
+ #ifndef ONLINE_JUDGE
+ freopen("input.txt", "r", stdin);
+ freopen("output.txt", "w", stdout);
+ #endif
+ ios_base::sync_with_stdio(0);
+ cin.tie(0); cout.tie(0);
+
+ ll n,q;
+ cin>>n>>q;
+
+ g.resize(4*n+6);
+ ar.resize(n+1);
+
+ for(ll i=1;i<=n;i++)
+ cin>>ar[i];
+
+ build(1,1,n);
+
+ while(q--)
+ {
+ ll t;
+ cin>>t;
+ if(t==1)
+ {
+ ll i,x;
+ cin>>i>>x;
+ update(1,1,n,i,x);
+ }
+ if(t==2)
+ {
+ ll lq,rq;
+ cin>>lq>>rq;
+ node temp;
+ temp=query(1,1,n,lq,rq);
+ cout<<temp.x<<endl;
+
+ }
+ }
+
+
+
+
+
+
+
+ return 0;
+}