Algorithms-I : 5-KdTrees: fix null pointer in KdTree

1 files changed, 10 insertions, 3 deletions

diff --git a/Algorithms/Part-I/5-KdTrees/KdTree.java b/Algorithms/Part-I/5-KdTrees/KdTree.java
index 73d9a90..bcf4609 100644
--- a/Algorithms/Part-I/5-KdTrees/KdTree.java
+++ b/Algorithms/Part-I/5-KdTrees/KdTree.java
@@ -100,7 +100,7 @@ public class KdTree
     // does the tree contain the point p?
     public boolean contains(Point2D p)
     {
-        if (root == null) return false;
+        if ((p == null) || (root == null)) return false;
         return get(root, p, true);
     }
 
@@ -113,7 +113,11 @@ public class KdTree
             cmp = Point2D.Y_ORDER.compare(p, n.p);
 
         if (cmp < 0)
+        {
+            if (n.left == null) return false;
             return get(n.left, p, !vsplit);
+        }
+        if (n.right == null) return false;
         return get(n.right, p, !vsplit);
     }
 
@@ -163,6 +167,8 @@ public class KdTree
     {
         Stack<Point2D> stack = new Stack<Point2D>();
 
+        if ((rect == null) || (root == null)) return stack;
+
         range(root, rect, stack, true);
 
         return stack;
@@ -191,10 +197,11 @@ public class KdTree
     // a nearest neighbor in the tree to p; null if tree is empty
     public Point2D nearest(Point2D p)
     {
-        if (p == null) return null;
-        if (root == null) return null;
+        if ((p == null) || (root == null)) return null;
+
         NearestChampion ncp = new NearestChampion(null, Double.MAX_VALUE);
         nearest(root, p, ncp, true);
+
         return ncp.p;
     }