I have to create a b-tree for an assignment, and I'm having trouble inserting into the tree. I'm hard coding the numbers 1-10, just to ensure they're being inserted in order. I already have the code (provided by my instructor) for splitting the root node once it's full and creating the left and right child. That's the insertRoot method.

The main problem I have is searching the tree to find what child to insert the next item to and also splitting a child node and promoting the middle element to the root. I've been working on it so long I'm at wit's end. Here's my code:

Tree Node class:

public class BTreeNode { public int[] key; public BTreeNode[] c; boolean isLeaf; public int n; private int t; public BTreeNode(int tnode){ t = tnode; isLeaf = true; key = new int[2*t-1]; c = new BTreeNode[2*t]; n = 0; }//end constructor }//end class

Tree Class:

public class BTree { BTreeNode left; BTreeNode right; int t = 3; boolean flag; int index; public void insertRoot(BTreeNode T, int newItem) { if(T.n == (2*t)-1){ left = new BTreeNode(t); left.n = t-1; for(int i=0; i<left.n; i++){ left.key[i] = T.key[i]; left.c[i] = T.c[i]; }//end left.c[left.n] = T.c[left.n]; left.isLeaf = true; right = new BTreeNode(t); right.n = t-1; for(int i=t; i<T.n; i++){ right.key[i-t] = T.key[i]; right.c[0] = T.c[i]; }//end right.c[right.n]= T.c[T.n]; right.isLeaf = true; T.n = 1; T.key[0] = T.key[t-1]; T.c[0] = left; T.c[1] = right; T.isLeaf = false; } treeInsert(T, newItem); }//end insertRoot public void treeInsert(BTreeNode T, int item) { if(T.isLeaf){ T.key[T.n] = item; T.n++; } else{ int ind = find(T, item); boolean result = isFull(T.c[ind]); if(result){ split(T.c[ind], T); } else{ treeInsert(T.c[ind], item); } treeInsert(T.c[ind], item); } }//end treeInsert public void printKeys(BTreeNode T) { if(T.isLeaf){ for(int i=0; i<T.n; i++){ System.out.print(T.key[i] + " "); } } else{ for(int i=0; i <T.n; i++){ printKeys(T.c[i]); System.out.print(T.key[i] + " "); } printKeys(T.c[T.n]); } }//end printKeys public boolean isFull(BTreeNode T){ if(T.n == (2*t)-1){ return true; } return false; }//end isFull public void split(BTreeNode T, BTreeNode root){ int mid = T.key[(0 + T.n) / 2]; root.key[T.n] = mid; BTreeNode x = new BTreeNode(t); x.n = t-1; for(int i=0; i<x.n; i++){ x.key[i] = T.key[i]; x.c[i] = T.c[i]; } x.c[x.n] = T.c[x.n]; x.isLeaf = true; BTreeNode y = new BTreeNode(t); y.n = t-1; for(int i=t; i<y.n; i++){ y.key[i-t] = T.key[i]; y.c[i] = T.c[i]; } y.c[y.n]= T.c[y.n]; y.isLeaf = true; root.n++; root.c[1] = x; root.c[2] = y; } public int find(BTreeNode T, int item){ if(item < T.key[0]){ index = 0; } else if(item > T.key[T.n-1]){ index = T.n; } else { for(int i=0; i < T.n; i++){ if(item > T.key[0] && item < T.key[i+1]){ index = i+1; } } } return index; } }//end

Main

public class Main { public static void main(String[] args) { int degree = 3; BTreeNode T; T = new BTreeNode(degree); BTree tree = new BTree(); tree.insertRoot(T, 1); tree.insertRoot(T, 2); tree.insertRoot(T, 3); tree.insertRoot(T, 4); tree.insertRoot(T, 5); tree.insertRoot(T, 6); tree.printKeys(T); } }