Range minimum Query - c++

Question

This is rmq using segment tree.
But i am not getting correct output can anybody tell me where i am wrong.
`
#include<iostream>
#include<cmath>
#define inf 1e9
using namespace std;
int get_mid(int a,int b){
return a+(b-a)/2;
}
int min(int a,int b){
int temp=(a<b)?a:b;
return temp;
}
int get_min_util(int str[],int beg,int end,int l,int r,int i){
if(l<=beg && r>=end)
return str[i];
if(l>end || r<beg){
return 0; ////////c1
}
int mid=get_mid(beg,end);
return (get_min_util(str,beg,mid,l,r,2*i+1),get_min_util(str,mid+1,end,l,r,2*i+2));
}
int get_min(int str[],int len,int l,int r){
if(l<0 || r>len-1 || l>r){
return 0;
}
else
return get_min_util(str,0,len-1,l,r,0);
}
int build_rmq_arr_util(int str[],int beg,int end,int big_arr[],int i){
if(beg==end){
big_arr[i]=str[beg];
return big_arr[i];
}
int mid=get_mid(beg,end);
big_arr[i]=min(build_rmq_arr_util(str,beg,mid,big_arr,2*i+1),build_rmq_arr_util(str,mid+1,end,big_arr,2*i+2));
return big_arr[i];
}
int*bulid_rmq_arr(int str[],int len){
int temp=ceil(log2(len));
temp=2*pow(2,temp)-1;
int *big_arr=new int[temp];
build_rmq_arr_util(str,0,len-1,big_arr,0);
return big_arr;
}
void pop(int arr[],int size){
for(int i=0;i<size;i++){
cout<<arr[i]<<" ";
}
cout<<endl;
}
int main(){
int str[]={1,2,3,4,5,6};
int len=sizeof(str)/sizeof(int);
int *rmq_arr;
rmq_arr=bulid_rmq_arr(str,len);
//pop(rmq_arr,3*len);
cout<<get_min(rmq_arr,len,1,2);
}
`
output of this code:
0
expected output in range 1-2 is 2
function get_min_util return 0 from if condition where comment ////////c1 is written

Answer 1

problem is in get_min_util().It should return infinity when not in range.Also you have to return minimum of left and right child.
int get_min_util(int str[],int beg,int end,int l,int r,int i){
if(l<=beg && r>=end)
return str[i];
if(l>end || r<beg){
return inf; ////////c1
}
int mid=get_mid(beg,end);
return min(get_min_util(str,beg,mid,l,r,2*i+1),get_min_util(str,mid+1,end,l,r,2*i+2));
}