Maximum distance between two 1s in a Binary Array in a given range

// C# program to find the maximum
// distance between two elements
// with value 1 within a subarray (l, r)
using System;

class GFG{
  
// Structure for each node
// in the segment tree
class node {
    public int l1, r1;
    public int max1;
}
static node []seg = new node[100001];
  
// A utility function for
// merging two nodes
static node task(node l, node r)
{
    node x = new node();
  
    x.l1 = (l.l1 != -1) ? l.l1 : r.l1;
    x.r1 = (r.r1 != -1) ? r.r1 : l.r1;
    x.max1 = Math.Max(l.max1, r.max1);
  
    if (l.l1 != -1 && r.r1 != -1)
        x.max1 = Math.Max(x.max1, r.r1 - l.l1);
  
    return x;
}
  
// A recursive function that constructs
// Segment Tree for given String
static void build(int qs, int qe, int ind, int []arr)
{
    // If start is equal to end then
    // insert the array element
    if (qs == qe) {
        if (arr[qs] == 1) {
            seg[ind].l1 = seg[ind].r1 = qs;
            seg[ind].max1 = int.MinValue;
        }
        else {
            seg[ind].l1 = seg[ind].r1 = -1;
            seg[ind].max1 = int.MinValue;
        }
  
        return;
    }
    int mid = (qs + qe) >> 1;
  
    // Build the segment tree
    // for range qs to mid
    build(qs, mid, ind << 1, arr);
  
    // Build the segment tree
    // for range mid+1 to qe
    build(mid + 1, qe, ind << 1 | 1, arr);
  
    // merge the two child nodes
    // to obtain the parent node
    seg[ind] = task(
        seg[ind << 1],
        seg[ind << 1 | 1]);
}
  
// Query in a range qs to qe
static node query(int qs, int qe,
           int ns, int ne, int ind)
{
    node x = new node();
    x.l1 = x.r1 = -1;
    x.max1 = int.MinValue;
  
    // If the range lies in this segment
    if (qs <= ns && qe >= ne)
        return seg[ind];
  
    // If the range is out of the bounds
    // of this segment
    if (ne < qs || ns > qe || ns > ne)
        return x;
  
    // Else query for the right and left
    // child node of this subtree
    // and merge them
    int mid = (ns + ne) >> 1;
  
    node l = query(qs, qe, ns,
                   mid, ind << 1);
    node r = query(qs, qe,
                   mid + 1, ne,
                   ind << 1 | 1);
  
    x = task(l, r);
    return x;
}
  
// Driver code
public static void Main(String[] args)
{
  
     
    for(int i = 0; i < 100001; i++)
        seg[i] = new node();
    int []arr = { 1, 1, 0,
                  1, 0, 1,
                  0, 1, 0,
                  1, 0, 1,
                  1, 0 };
    int n = arr.Length;
    int l = 3, r = 9;
  
    // Build the segment tree
    build(0, n - 1, 1, arr);
  
    // Query in range 3 to 9
    node ans = query(l, r, 0, n - 1, 1);
    Console.Write(ans.max1+ "\n");
}
}
 
// This code is contributed by Princi Singh