Implementation of Segment Tree

/* Creating a segment tree. Then with the query() we can easily find the sum of any segment of the tree. */ #include<bits/stdc++.h> using namespace std; #define mx 100001 #define fi(a, b) for(int i=a; i<=b; i++) #define fd(a, b) for(int i=a; i>=b; i--) int n, m, ar[mx], tree[mx*3], ii, jj; void segmentt(int node, int st, int en){ if(st==en){ tree[node]=ar[st]; return ; } int left=node*2; int right=node*2+1; int mid=(st+en)/2; segmentt(left, st, mid); segmentt(right, mid+1, en); tree[node]=tree[left]+tree[right]; } int query(int node, int st, int en){ if(ii<=st && jj>=en) return tree[node]; // relevant segment else if(ii>en || jj<st) return 0; // out of the segment else{ // needs to divide again int left=2*node, right=node*2+1, mid=(st+en)/2; return (query(left, st, mid) + query(right, mid+1, en)); } } int main(){ cin>>n; fi(1, n) cin>>ar[i]; segmentt(1, 1, n); cin>>m; fi(1, m){ cin>>ii>>jj; cout<<query(1, 1, n)<<endl; } return 0; }