Dynamic segment tree leetcode six hundred and ninety-nine

// Dynamic segment tree 
public class DynamicSegTree {
    private Map<Integer, Integer> tree;// Line segment tree , Represents the value of a node 
    private Map<Integer, Integer> lazy;// Lazy mark 
    private int N;// Maximum range 
    public DynamicSegTree() {
        tree = new HashMap<Integer, Integer>();
        lazy = new HashMap<Integer, Integer>();
        N= (int)1e9;
    }
    // Interval modification 
    public void update(int l,int r,int val){
       if(l>r) return;
        update(l,r,1,N,1,val);
    }
    private void update( int l, int r,int curl, int curr, int node,int val) {
        // Interval no intersection 
        if (curl>r||curr<l)
            return;
        // The current interval is within the target interval 
        if (l<=curl&&curr<=r) {
            tree.put(node,val);// Update current node 
            if(curl<curr) lazy.put(node, val);
        } else {// There is an intersection between the current interval and the target interval 
            int mid = (curl + curr) >> 1;
            if(lazy.getOrDefault(node,0)!=0)
                pushDown(node,lazy.get(node));// Pass tag down 
            // Split processing interval 
            update( l, r, curl, mid,2 * node,val);
            update(l, r, mid+1, curr, 2 * node + 1,val);
              // Update current node 
            tree.put(node,Math.max(tree.getOrDefault(2 * node, 0),
            tree.getOrDefault(2 * node + 1, 0)));
        }
    }
    // Pass the tag to the next level 
    private void pushDown(int node,int _lazy){
        lazy.put(node*2,_lazy);
        lazy.put(node*2+1,_lazy);
        tree.put(node*2,_lazy);
        tree.put(node*2+1,_lazy);
        lazy.put(node,0);
    }
    // Interval query 
    public int query(int l,int r){
       if(l>r) return -1;
        return query(l,r,1,N,1);
    }
    private int query(int l,int r,int curl,int curr,int node){
        // Not in the target range 
        if(curl>r||curr<l)
            return 0;
        // In the target range 
        if(l<=curl&&curr<=r)
            return tree.getOrDefault(node,0);
        // Some have intersections , Split interval processing 
        int mid=(curl+curr)>>1;
        if(lazy.getOrDefault(node,0)!=0)
            pushDown(node,lazy.get(node));
        return  Math.max(query(l,r,curl,mid,node*2),query(l,r,mid+1,curr,node*2+1));
    }
 
 
 
}
 
 
    public List<Integer> fallingSquares(int[][] positions) {
        List<Integer> ans=new ArrayList<>();
        DynamicSegTree t=new DynamicSegTree();
        for(int[] position:positions){
            int max=t.query(position[0],position[0]+position[1]-1);// Query the maximum value of the block interval 
            // Update block interval 
            t.update(position[0],position[0]+position[1]-1,max+position[1]);
            ans.add(t.query(1,t.N));
        }
        return ans;
    }