Segment tree GSS3 & GSS1

First of all read about segment tree and it basic functioning. You can read it from HERE .

Given below code is for GSS3 & GSS1 spoj .

Here i have implemented segment tree as given in above link.

//for GSS1 remove update part from main function

#include <bits/stdc++.h>
using namespace std;
#define INT -1000000
int k;
struct node
{
    int result,pre,suf,sum;
    void split(node &a , node &b){}
    void merge(node a , node b)
    {
        sum = a.sum + b.sum;
        pre = max(a.pre , (a.sum + b.pre));
        suf = max(b.suf , (b.sum + a.suf));
        result = max(a.suf + b.pre,max(a.result , b.result));
    }
    node()
    {
        result = pre = suf = sum = INT;
    }
    node(int temp)
    {
        result = pre = suf = sum = temp;
    }
}tree[131080];
void update(int pos)
{
    pos>>=1;
    while(pos!=0)
    {
        tree[pos].merge(tree[pos*2],tree[pos*2 + 1]);
        pos>>=1;
    }
}
node range_query(int root , int left_most , int right_most , int l ,int r)
{
    if( l <= left_most && r >= right_most )
        return tree[root];

    int l_child = (root<<1) , r_child = l_child + 1 , mid = (left_most + right_most )>>1 ;

    tree[root].split(tree[l_child],tree[r_child]);

    node l_node = node() , r_node = node();

    if(l <= mid)
        l_node = range_query(l_child , left_most , mid , l , r);
    if(r > mid)
        r_node = range_query(r_child , mid + 1 , right_most, l , r);

    tree[root].merge(tree[l_child] , tree[r_child]);

    node temp = node();
    temp.merge(l_node,r_node);

    return temp;
}
int main()
{
    int n,temp,l,r;
    scanf("%d",&n);
    k = ceil(log(n)/log(2));
    int pos = (1<<k);
    int a[n];
    for(int i=0;i<n;i++){
        scanf("%d",&temp);
        tree[pos+i] = node(temp);
        update(pos+i);
    }
    int m,c;

    scanf("%d",&m);
    while(m--)
    {
        scanf("%d%d%d",&c,&l,&r);
        if(c==1)
            printf("%d\n",(range_query(1,1,pos,l,r)).result);
        else if(c==0)// Update part-> remove this condition for GSS1.
        {
            tree[pos+l-1] = node(r);
            update(pos + l -1);
        }
    }
    return 0;
}