including description and edge test cases for inserting duplicate keys, deleting non existent keys, Handling empty tree and Inserting and deleting keys that cause multiple splits or merges

Author: skamble2

src/main/java/com/thealgorithms/datastructures/trees/BTree.java

@@ -13,11 +13,68 @@
  */
 
 public class BTree {
+    private BTreeNode root;
+    private int t;
+
+    public BTree(int t) {
+        this.root = null;
+        this.t = t;
+    }
+
+    public void traverse(ArrayList<Integer> result) {
+        if (root != null) {
+            root.traverse(result);
+        }
+    }
+
+    public BTreeNode search(int key) {
+        return (root == null) ? null : root.search(key);
+    }
+
+    public void insert(int key) {
+        // Prevent duplicate insertions
+        if (search(key) != null) {
+            return;
+        }
+
+        if (root == null) {
+            root = new BTreeNode(t, true);
+            root.keys[0] = key;
+            root.n = 1;
+        } else {
+            if (root.n == 2 * t - 1) {
+                BTreeNode s = new BTreeNode(t, false);
+                s.children[0] = root;
+                s.splitChild(0, root);
+
+                int i = 0;
+                if (s.keys[0] < key) {
+                    i++;
+                }
+                s.children[i].insertNonFull(key);
+                root = s;
+            } else {
+                root.insertNonFull(key);
+            }
+        }
+    }
+
+    public void remove(int key) {
+        if (root == null) {
+            return;
+        }
+
+        root.remove(key);
+        if (root.n == 0) {
+            root = (root.leaf) ? null : root.children[0];
+        }
+    }
+
     static class BTreeNode {
         int[] keys;
-        int t; // Minimum degree (defines range for number of keys)
+        int t;
         BTreeNode[] children;
-        int n; // Current number of keys
+        int n;
         boolean leaf;
 
         BTreeNode(int t, boolean leaf) {
@@ -48,10 +105,7 @@ BTreeNode search(int key) {
             if (i < n && keys[i] == key) {
                 return this;
             }
-            if (leaf) {
-                return null;
-            }
-            return children[i].search(key);
+            return (leaf) ? null : children[i].search(key);
         }
 
         void insertNonFull(int key) {
@@ -80,7 +134,6 @@ void insertNonFull(int key) {
         void splitChild(int i, BTreeNode y) {
             BTreeNode z = new BTreeNode(y.t, y.leaf);
             z.n = t - 1;
-
             System.arraycopy(y.keys, t, z.keys, 0, t - 1);
             if (!y.leaf) {
                 System.arraycopy(y.children, t, z.children, 0, t);
@@ -109,11 +162,9 @@ void remove(int key) {
                     removeFromNonLeaf(idx);
                 }
             } else {
-                if (leaf) {
-                    return; // Key not found
-                }
+                if (leaf) return;
 
-                boolean flag = idx == n;
+                boolean flag = (idx == n);
                 if (children[idx].n < t) {
                     fill(idx);
                 }
@@ -208,7 +259,6 @@ private void borrowFromPrev(int idx) {
             }
 
             keys[idx - 1] = sibling.keys[sibling.n - 1];
-
             child.n += 1;
             sibling.n -= 1;
         }
@@ -218,7 +268,6 @@ private void borrowFromNext(int idx) {
             BTreeNode sibling = children[idx + 1];
 
             child.keys[child.n] = keys[idx];
-
             if (!child.leaf) {
                 child.children[child.n + 1] = sibling.children[0];
             }
@@ -267,54 +316,4 @@ private void merge(int idx) {
             n--;
         }
     }
-
-    private BTreeNode root;
-    private final int t;
-
-    public BTree(int t) {
-        this.root = null;
-        this.t = t;
-    }
-
-    public void traverse(ArrayList<Integer> result) {
-        if (root != null) {
-            root.traverse(result);
-        }
-    }
-
-    public boolean search(int key) {
-        return root != null && root.search(key) != null;
-    }
-
-    public void insert(int key) {
-        if (root == null) {
-            root = new BTreeNode(t, true);
-            root.keys[0] = key;
-            root.n = 1;
-        } else {
-            if (root.n == 2 * t - 1) {
-                BTreeNode s = new BTreeNode(t, false);
-                s.children[0] = root;
-                s.splitChild(0, root);
-                int i = 0;
-                if (s.keys[0] < key) {
-                    i++;
-                }
-                s.children[i].insertNonFull(key);
-                root = s;
-            } else {
-                root.insertNonFull(key);
-            }
-        }
-    }
-
-    public void delete(int key) {
-        if (root == null) {
-            return;
-        }
-        root.remove(key);
-        if (root.n == 0) {
-            root = root.leaf ? null : root.children[0];
-        }
-    }
 }